It was kind of true a very long time ago except in potato quality. And if you were out of data, but was connected on WiFi instead, you actually couldn't. And you still can't text a large video across the Android / iPhone chasm, can you?
I'm regularly sending/receiving gifs and decent quality short videos between iOS and Android these days.
The quick explainer is phones send a user agent with the request to fetch a media message, this user agent contains a link to a file that describes what the device can handle. Apple and Blackberry hosted these files themselves, Verizon hosted most of the android ones on its network itself. They decommissioned the server hosting them a few years ago which made it so all affected devices pulled the lowest potato quality image down for compatibility. Huge number of complaints.