My bank (actually a credit union, but a big one, which works great for me as my only Bank) recently updated their online services and mobile app. As part of the update they required a sort of two factor ID (one time only) via phone. I encountered the same issue, my RW number was listed somewhere as VoIP, so “cannot use it.”
My home phone number was fine, although that is also completely VoIP (albeit a Bell Telephone number transferred a few decades ago).
I will push on my credit union to correct this, although i am sure any technical understanding is at least a couple steps (and likely service supplier companies) away from the customer service or management people I can access directly. OK for now, but just wrong, and a pain. So any additional basis or facts about why or how RW numbers should not be so discriminated against will be valued.