I'm a little confused on your description. You say the primary point of difference is in being able to send and receive picture messages, but can't you do that in any messaging app as well?
Only to other users of the same messaging app. This is a mobile phone number that works with any other mobile phone number for voice calls, txt and picture messages. There are about 10 apps that do this in North America (the most start uppy of which is OpenPhone) but zero apps that do this outside of North America (apart from BenkoPhone).
BenkoPhone users can send each other messages and pictures (and other files) directly, just like WhatsApp or Signal or whatever, but when they send to a mobile number that is not hosted by BenkoPhone it will go out over the mobile network, a bit like how when you send a picture to an Android user from iMessage it goes as an MMS but if you send to another iMessage user it goes via Apple's internal messaging.
BenkoPhone users can send each other messages and pictures (and other files) directly, just like WhatsApp or Signal or whatever, but when they send to a mobile number that is not hosted by BenkoPhone it will go out over the mobile network, a bit like how when you send a picture to an Android user from iMessage it goes as an MMS but if you send to another iMessage user it goes via Apple's internal messaging.