It depends on your angle of security concern.
For example,
1. it's a noncustodial wallet, giving you full control to your funds. Nobody should ever use a close sourced wallet.
2. It's not open source, that's if you want to audit and analyze the source code. They also have
their reasons for being close sourced.
3. They several financial licenses plus KYC and AML providers for their exchange services, perhaps. So you are sure they are complying with authorities and there won't be any witch hunt
You could read through
Cryptocurrency was created to be transparent that everybody can check the open code.
When community can check the code it will be more trust to the project.
Do you think so?
Many wallets use onen code.
What is your main reason that you do not use open code?