I have been prone to hypos for decades (reactive hypoglycaemia), and always resisted family and peer pressure to give blood.
I am too concerned it would trigger a hypo.
Of course I will never know if my concern is justified, but i'm never going to test the theory.
No idea if there could be similar issues for T1s, or not.
Edited to add: mind you, stuck up a mountain, after a plain crash, with someone bleeding out in front of my eyes, i would change my mind in a second.