It's not about wasting more time, it's about doing different kinds of training, you just learned to shoot about head level, nothing more, not really improving reaction, all bots on same surface. Hsdm makes you compete with real players and shoot faster/more precise as they spawn everywhere on the map and about to be as good as you, so you should go even further. That circle shit map makes you more concentrated on shooting, it's a complex map for aim/fast aim, reaction, distance.
I'm pretty sure it's about making training complexed, to put use of your aim in any situation.
Like 5-15 minutes map with circles, 15-30 any map with bots and then 25+ on hsdm/dm until you feel ready. Not too exhausting.