Dude I already told you that everything in Trezor3 is OPEN SOURCE including secure element, so I don't know what more do you want? Some certificate approval?
btw you are using devices with closed source chips all the time in your credit cards, smartphones, computers, etc.
I am not sure why you are comparing a centralised chip with a decentralised and non-custodial secure chip. Both are different; credit card chips won't be open source because they are centralized. When you get a credit card, you already trust them. But for a hardware wallet, this isn't a fact. Do you know private keys would be revealed from the Secure Element Chip through a firmware update? If you don't know, then search for it. The manufacturer could reveal the stored data to Secure Chip through a firmware update if they want it. This is the reason I am leaving the Ledger wallet. But the good thing is that Trezo firmware is open source, and if they implement something like revealing private keys through firmware updates, then the community could detect it.
So most likely, I am going to order Trezor Safe 3, which is universal.