Uchideshis have to be strong.
Aikidoists are athletes. And they have to undergo basic training not only to build their strong core but to nurture strengths in their muscles around their knees and waist so that they will endure suwariwaza and koshi-nage.
Anyone who tends to repeat taking flamboyant ukemi, including the kind of ukemi that falls on one’s back, without fundamental physical strengths, they are more likely to sustain bodily ailments in their later years.
Any instructor who throws their students as their ‘uke’ without any regard to, or consideration for, their uke’s physical conditions today and of their future, it might be that they should not be regarded as good instructors.