To quote Shioda Sensei's Total Aikido (pp 125), "As you advance forward with the right foot along the diagonal line to uke's rear..."
If you have a chance to look at the book, it has very clear 'top view' pictures of tori and uke. Uke ends up falling more towards the 'outside' as tori enters towards the 'dead corner' of uke.
I think the other Student is referring to directly facing uke and entering, rather than moving in a diagonal behind uke. If you are looking at uke face-to-face and enter, it is much easier for uke to pull you down with him. Uke also ends up falling more towards the inside or directly in front of tori (which can be dangerous).
I hope this helps.
I'm returning a favor that someone else did for me in another thread about iriminage