No he didn't preform. Most of his offspring didn't preform either because why should they... That was at the beginning of the specialization, they didn't need to perform, they earned enough money without doing anything more, just like the specialization that is still going today.
I bet you would be very surprised at how many performance horses in every discipline have Impressive in their pedigrees. (No I don't have a figure for you)
As for Impressive having too much muscle to perform, he had less muscle than Poco Bueno. He was not overly muscled or very big either at barely 15 hands. He just happened to be well sculpted naturally because of the HYPP thing which is another reason for why he didn't run on the track or preform. The specialization craze has added the muscle and bulk on the halter horses, not Impressive. Bigger is better right... Not. They do that in the dog world too.