Not to mention that a lot of legitimate crypto wallets are open-source in the first place lol.
Exactly. When talking about open source software, the idea is to use what is good in other products and add in your own, or even fork good products code.
This makes absolute no sense, as good wallets are most of them open source, such as Electrum.
I know multicurrency wallets are usually closed-source, and Trust Wallet is an exception (probably the best of those). You can just clone their repository, no need to buy a white label wallet..