1.31 PTR was more buggy than the release of the real 1.31. The real 1.31 itself very buggy, so the PTR version of it is probably not the best choice if you are looking to downgrade. That post is relevant on the blizzard forums because most players there probably do not use hiveworkshop, but anyone who uses hiveworkshop can easily use search to find the threads with 1.30.4 and 1.29 downloads (the two most stable patches in my opinion).
If they do make custom campaigns require an online connection, it will likely be because people can extract the normal WCIII campaign and port it as a custom campaign, and if offline access is easier to crack than an online access requirement, then blizzard's sales would be affected since people could then in theory play the wc3 reforged campaign without buying the game (still assuming offline access is easier to crack).
Thinking that they will monetise custom campaigns is a little far fetched.
