To be very clear – it is impossible for @Trezor to release the "first open-source secure element on the market" if they are not using the OpenPDK at Skywater foundry (130nm process or maybe 90nm when available).

TropicSquare prototypes are made at UMC in Taiwan – their PDK (process design kit) is closed source, meaning that parts of the chip will be closed source.

I am growing tired of so many Bitcoin and crypto companies wielding the term "open source" for marketing purposes while slowly diluting the definition.

It is fair to say that TropicSquare will have an "open architecture" and that parts of the chip will be "open source" – but this will not be a panacea or the "first open-source secure element."

The best project building an open source Secure Enclave is https://betrusted.io which uses an FPGA to run a simulated RISC-V chip in which the entire simulated chip is open source.

Otherwise there are no good efforts.

If we @FOUNDATIONdvcs were to build an actual open source secure element chip, we would do something very simple at 130nm or 90nm at Skywater using their OpenPDK – and open source the entire chip.

Fair, this is statement from soc media manager and it is missing nuances.
 
When you dig into Tropic Square docs, you'll see they are honest about not being *fully* opensource. But the digital design (and everything designed by Tropic Square inhouse) will be fully open source.