Why aren't transformation ultimates not cancelable with stuns?

[Devil-26652]

@Ghostrick-11458

Snowball midair I’ll do you proud Mei!

Mei: Flashbanged

Snowball: God Mei you’re such a disappointment. disappears

This can be mostly blamed on latency and favor-the-shooter:

[PROOF] Projectile Ults blocked by Lag

Hello everyone, Today do I want to prove to everyone that projectile ultimates can disappear after it being cast. That projectile ultimates can disappear mid-air. I’m going to use Mei’s ultimate as an example in this thread because that one has the longest cast time among the projectile ultimates. I will add a TLDR at the bottom of this thread.

Also, If you click on this text with the arrow,

will you see a video about it. I've put it in a 'detail' box to have a cleaner post and to…

I just don’t understand why transformation ultimates get a free pass from stuns.