I'm trying to imagine the average grunt pulling an armored fellow down and pulling off his visor to see if he's a man at arms or a noble. But probably not even knowing who he is and half pissing his pants because the armored man's mates are rushing across the battlefield after him. I imagine it had a whole lot less "who is this guy" and more like "f~%!! f@%!! draw my dagger! Shank his nuts! Codpiece! Stab his eyes! Stab his eyes! God why is he still screaming! Stab him again! I really don't want to be here!"
I reckon that people being captured would more likely be the result of a deliberate effort on behalf of a few canny fellows and orchestrated through their thugs. Some savvy operator picks Mr Knight as being Sir Fancypants of Walmart and words up his cronies to rush the guy and pull him down, take him alive for a bit of a payday.
That would make more sense to me. HAve five guys drag him off his horse and off the field before anyone was the wiser. Bonus to the large burly fellows willing to lay hands on a highly trained, well fed, and very angry blue blood.
The suit on the left is a normal suit of armor, probably for someone like 5'6" (~167cm). The tall suit as I recall was worn by some Austrian knight and he would have been close to 8' tall. Now that would have been something to see on the battlefield.