It's really unfortunate that there is a bunch of misunderstood concepts going on here.
When DirecTV talks about having any sort of Internet access, it is for VoD (Video on Demand) as well as if you use your STB for app access.
4K, if it's using an Internet connection, is severely compressed down to your box. I'm not saying that's a bad thing, but I am saying that uncompressed 4K would actually take a 12GB link -- you can see the difference there.
Typically, HD-based programming really only requires about 5MB so that you don't drop frames or run into pixelation, etc., so that's probably why DirecTV is recommending 25MB.
So, unless DirecTV is intentionally hijacking their own boxes that are provisioned for 4K so that they require an Internet connection, the 4K that you receive is coming off the sat feed, not the Internet (with VoD exception, and that'll be compressed anyway).