Why is Tangem-Wallets firmware closed source?!

Does it have any benefits or reasons? I dont find any functionality that comes with closed source. Aren't Hardware wallets all about not having to trust another party and being in full control of your own cryptos? Why would a Company Not want the publicity to know about the Code integrated in their "safe" product. And i am always hearing all These affiliate youtubers bragging about the tangem app being open source, but isnt that completely irrelevant if the firmware is closed? I really love the idea of the wallet being a card and the extremely intuitive and easy app Design, plus tangem Supports every Coin which i am currently holding which is great. But i am probably still gonna buy a trezor although it doesnt Support every Coin i need. If there is any reason why the closed source firmware is 100% harmless please enlighten me. Thank you!^{^}