Maybe work phone vs personal phone? My DH primarily uses his work phone, even for personal email/texts, but is not allowed to have WhatsApp on his work phone for security reasons. So he only uses WhatsApp on his personal phone (family/friends in Europe).

Maybe. But it could be a google phone number, or any other of the myriad of apps available that give you alternate phone numbers.

I use an alt on whats app for dating, because people are crazy. I don’t move to texting on iMessage until things have progressed (if they do).

This seems to be the opposite. You could just ask.

I met a man and was texting him on his mobile number. Later, he asked me to text him via WhatsApp. I noticed a different phone number shows up for him on WhatsApp. Does this mean he’s using a burner phone?