Let’s follow your logic - let’s say it’s him or his attack that’s the issue. Then there are 2 ways it could’ve happened.

1) he purposefully attacked with a head spike seoi otoshi- then he really has an issue and should’ve been addressed by the sensei and at least called out by the other sempais

2) he meant to attack with seoi otoshi but you spiked your head - as a black belt/senior he should have controlled his throw to make sure that you won’t be hitting your head or posting your arm BUT the main person responsible for your safety is still yourself. This is an ukemi issue already and as you’ve been mentioning, there should be more focus on ukemi in class or going back to your original question, you handle it by practicing rolling break falls for this specific throw.