You don't need to have your work communication on your private phone. If you want to do that, you can still temporarily disconnect them before leaving for holidays...
That statement makes a few assumptions. I don't have more than one device for this stuff. My business and clients all emergency numbers (which would include that person number if it existed). I also have a painfully small amount of self control and have in the past nipped off to check my emails for "10 minutes".
A holiday can be a good opportunity to disconnect completely.
When I go on holiday, I don't want business calls and emails following me. If I need to make a call, I'm sure I'll find a way to make it.