MMA-block Hmmm. I think you got a canned first-level response. An MTE crash dump is not a deployable vulnerability. An interested party might start with an MTE crash dump, but they would need to experiment a fair amount (which you are presumably not doing).
I think it is not wrong to encourage people getting MTE crashes in Proton products to report them to Proton. Posting lots of crash dumps online might not be as friendly, though.
Edit: meanwhile, honestly it seems to me it would be responsible for them to test on GrapheneOS. Just my opinion, though!