This is the part that you get wrong. We're not trying to justify anything or convince anyone about anything. We just set the record straight because you were reproducing inaccuracies. And you should definitely not use Coinomi if you don't feel confident about it, and the same goes for all wallet services out there, open-source or not.
You make a good point because before someone will decide to use a wallet he needs to reassure his coins are safe with the wallet he want to use and this is the reason why open source wallet are hot cake within the crypto community because the community will have the chance to review the wallet code and check is theres any malicious module, drawbacks, hidden code etc.