...Am I the "uke from hell" because I have a strong grip and are well centred?
Nah, a well-centred uke with a strong grip is the easy kind. If you have a strong and stable centre and you grip hard it gives nage a direct and easy communication with your centre, and enables them to manipulate it - so long as nage knows what they are doing. But being that sort of uke isn't so good for beginners IMO, it can cause them to get discouraged because they haven't got out of the mindset of making
the waza work, as opposed to allowing
the waza to work.