I am also a fellow Yoshinkan student, and also new at that. I don't know who's at a higher level, you or me, but I will attempt to answer your question anyhow, and you can decide what to take away from it.
I am training at the Sokushinkan Dojo in Vancouver, and not long ago Andrew McBride sensei showed up at our dojo and began teaching us regularly in addition to our dojocho, Keith Taylor sensei. Andrew sensei is a yondan, and a senshusei graduate. If you did your research, then you probably know about senshusei. Needless to say then, he is very skilled at both applying the techniques and in teaching them. Being a graduate of that hell camp, he is very big on basics, such as kamae and kihon doza.
His way of explaining, and that goes for all my sensei's, is that there is only one kind of kamae, and you do nothing but that at Yoshinkan. Students who gets creative with the stance don't get very far. The idea behind the kamae and the kihon doza is very deep, and so students like us won't get it right away. But in order to one day grasp the meaning behind it, you must not deviate from the standard.
Later on at godan and beyond, your kamae will be in everything. It won't matter how you stand, because you will know how to control your centre. But at our stage of training, we need to have the correct form in order to start learning how to become aware of that centre.
Yoshinkan is unique among other styles of Aikido in that we focus on correct form first, rather than timing and flow. Shioda sensei feels that doing timing and flow first is like trying to write cursive before standard blocky scripts. It won't be very good and no one can understand it.
Kamae is done like so:
put your front foot directly forward, then put your back foot 90 degrees to it. Then, slightly rotate the front foot 30 degrees to 45 degrees to the outside, and bring up the back foot by the same angle. Now the foot should be in a V shaped position. The distance between your foot should be average stride distance, or you can check by kneeling down on the back leg's knee. The knee should be in line with the middle of the front foot. Bend your knees forward and distribute weight at 60/40, at the same time straighten your back leg and have it locked at the knee. Keep the waist squared to the front, and the shoulders relaxed with armpits closed (should be able to hold a tea towel in there). raise the arm that is the SAME side as your front foot to chest level (not shoulder), with the arm slightly bent, just the same shape as when the arm is hanging freely. the other arm goes down towards the obi, and at one fist distance from the knot. Both hands should have some tension on the forearm, and fingers spread apart flat and open. The hands should be aligned to your centreline, same as your feet, as if you are holding a panel of glass. Both hands should have the ring finger parallel with the ground, and so the lower hand must bend a lot. This should resemble the position of holding a sword. Then, bring your head back so that the back is touching the collar of your dogi, and keep your head level and looking forward. This will straighten the spine and keep your balance centred, resulting in an axis that runs down your centre of balance. Finally, engage your hips by pushing it forward so that there is a curve at the small of the back, and your knot on the belt should be point diagonally downwards.
In other words, your sensei is correct. The fingers should be tense though, not totally relaxed. The only problem is the senior students, who seems to differ from your sensei.
However, there is a possible and very simple explaination for this: they are trying to train you
The 90/10 is the weight distribution for high power throws. By doing kamae at this form, you increase your flexibility and strength/endurance of the muscles that are used for Aikido. Your blackbelts will tell you to do this so that you get stronger as you go. The sensei's form is the correct kamae, but it won't make you as strong as fast. The legs will naturally shift at the foot and the knees do to the sink in, but that is natural and expected. You shouldn't follow the blackbelts who raises the arm opposite to the front foot, nor should you have your foot pointing inwards like an A. Those aren't kamae or permutations of it, but experimental stances that won't work. There is a lot of things to watch for in kamae and the lower sinkdown versions, but essentially it's this: at 60/40, your knee should be inline with the front foot, at 80/20 your knee should be one fist apart from the front foot, and at 90/10 it should be two fists distance apart.
If you wish to be certain, ask your sensei, but the 90/10 is training you to be stronger and more flexible.
Andrew sensei will sometimes press diagonally down on the small of our back to force us to work harder to hold kamae. It will make your muscles scream bloody hell, but you'll get strong real fast.
Hope this helps clearing up some confusion, and remember: when in doubt, do it hombu style!