Ignoring whether or not there could be backdoors, security holes in the Trusted Execution Environment stuff are still being found on a regular cadence.
I'd guess it's good enough to avoid bulk surveillance (and therefore extraction of training data, which I guess is the attack that Notion was running when they screwed up and leaked the data), but that's about it.
Apple's stuff is a similar story. (And so are VM enclaves, which have been around longer.)