How to set up restrictions to allow WhatsApp which is 13+ when restrictions only offer 12+ or 17+

I have setup content restrictions for my 14 yr old on his iPhone and given the choice between 12 or 17, I chose 12+.

WhatsApp requires 13+.

Anyone found a way around this without allowing access to 17+?

I’ve tried temporarily using 17+ to install, but the moment I revert to 12+ the app is removed.

Seems a problem for (one of) the most popular messaging apps out there.

TIA,

[Re-Titled by Moderator]

Original Title: WhatsApp 13+ but Content restrictions 12+ or 17+