Oh I don't just think it's made up, I know it's made up. There's a reason nobody outside of right-wing internet circles (and occasionally Sean Hannity) uses the term they co-opted, and it's not because of some silly conspiracy like "muh MSM" trying to push it down and "hide the truth", it's because nobody else takes their made up term seriously.
But it makes sense that someone who thinks anarcho-communists want a state (lol!) would also be just as easily fooled into believing the term "alt-left" is anything other than a strawman of everyone to the left of the average D, used by baby alt-righters and alt-lites to convince themselves they're of neither extreme and are just peaceful-minded "freedom fighters". Either that, or it's because they're too lazy to actually educate themselves on the difference between liberals, marxists, and anarchists, so they just decided to conflate them into one big group to make things easier on themselves. Based on your assumption mentioned above, I'm going to assume you're either of the latter or both.