I see no purpose or sense in it. Some of those guys who almost do it 'professionally' to post up, I truly doubt if a cock that is 10 inches in circumference can truly get erect, OR spew out cum like they pretend to show it does.
As far as other pumping 'injuries' typical for me is after pump 'plump' mid dick, which is just fatty tissues and lymph that got sucked up too much. Looks and feels awful.
But an over pump can also leave a scab like blister somewhere on the tip of your dick. I had pumped up (on purpose) a day before my annual visit to my dermatologist. She and her other female assistant to a total naked body exam on me, looking for any sun blisters or possible cancerous hot spots, normally on my back or arms. But my dick was pumped just a bit yet when I arrived, and I had that little blister on the tip of my cock. So I asked her "what about this here?",,pointing out that blister on my dickhead. The two of them took a hold of my cock and moved skin around to see what was going on for my cockhead. I just love when both of them check out my dick! Her final analysis was " see your primary care doctor, as it looks like herpes'. LOL,,, I know I dont' have herpes and never will. She apparently has no knowledge of mens cock pumping results and what small 'injuries' might show up in skin exam. That was a fun visit,, certainly worth my co-pay !! Surprised she didnt' schedule me to come back in a week to check out my cock once more.