Does that help against an attacker determined enough to hack you that he'll pay $1000 for a SIM swap? Surely he has channels to figure out your "secret" phone number since you registered it with the service he's trying to hack into.
The trouble with compartmentalizing with a separate phone is that the company with your money probably also sold your secret phone number (that they only required for security) so it will probably also show up on that whitepages site.
There is also that some services don't accept foreign numbers for authentication. Nor virtual phone numbers.
But it adds a layer of protection, doesn't it? Your known public phone number is one, your verification phone is another one from another carrier.
Is that really an additional layer of protection, or the same layer, slightly obscured? But probably not obscured from the attacker that managed to get your password and just needs the SMS verification code to get into your account.