If it matches the "low effort task" definition (outlined here:
https://bitcointalk.org/index.php?topic=3953664.0) then yes. In this case, they not only incentivised posting via low effort tasks but also incentivized posting in their (now trashed) ANN thread.
How do you prefer them to be reported? Reporting one post at a time through the report button takes me a lot of time, and feels boring enough to quickly give up. Barely any of them use a "normal" forum name, most look like they're generated by bots. And bots won't care about temp bans.
I can report them, but if a report just leads to that one post being deleted, it doesn't seem worth the effort. If they get nuked, at least that account won't do it again.
In the past 5.5 days, 3194 Newbies have posted "#join". In the past 15 hours, there were "only" 248 Newbies who posted "#join":
-data snip-
Generally just reporting the giveaway itself is enough. Also, posting "#join" in itself is not bad - plenty of threads use the "#join" format for applying to non-low effort tasks (e.g. signature campaigns).