Then 7 reps from bottom to top and then 7 full rep so 1 somplete set of 21?
Or simply doing half reps to 90degrees?
You could ask them why they are doing what they are doing?
of its several guys then they must have got the same playbook somewhere

If its just a couple,maybe 1 dude did it and anotherbis teting to copy ?
How do they look? Do their physiques look like they know what they are doing?

Are they working through an injury?
are they just ignorant or is their purpose.
I try not to judge people in the gym unless I ask them or know for a fact what they are doing is harmful or plain dumb

You mentioned curls with shoulder sway, for every rep..dumb.
But for onjury bicep anchor...not so much.
And for extra reps to help withbth3 3cxenyric part of the lift also not dumb,but smart.

So it depends..the same lift czn be done for a purpose that is effective or wrong and less effective because its not being done for the purpose that makes it effective, and is also harmful if done improperly. thus not done correctly.

Crossfit stuff comes to mind...maybe those guys are crossfitters?