I remember those 88 and 89 matches very well, especially in 88, my 1st Jr Wimbledon! I clearly remember the conditions were cloudy and colder and thus slower the last few days, and in the semis, Edberg came back from 0-2 down against Mecir in a wonderful spanking by Mecir for 2.5 sets, then Edberg somehow just held his nerve for Mecir to tire and get nervous.
The finals were cloudy too, but Becker started big and fast, winning that first set. Edberg kept calm and stayed with Becker into the tb, where he won with his backhand returns, especially the 1st serve bunt return which set up his volley. Becker served to Edberg's forehand and his mishit the return but anticipated well and ripped the passing shot with confidence. Becker just lost his "I've got this!" composure immediately. That tiebreak is still etched in my mind as my coach was telling how his backhand side won that tiebreak, with the help of 4 big 1st serves. He missed 2 forehand returns entirely.
In 89, the sun was out and it was a little faster. Edberg also changed his service motion from the year before, abbreviating his take back a little, from his injury in the AO against Lendl. Becker just blasted everything coming out of the gates and made Edberg look like a passenger in that bagel 1st set. Edberg had 3 set points in the 2nd at 6-5 but lost it , and it was a blowout in the breaker.
90 I was there in center court as a graduation present, and I remember Becker playing like he was drugged for 2 sets, that's what the nice lady in front of me said!
Then he started playing better and just pushed Edberg back. Only late in the 5th set did Edberg finally show up. It wasn't the best tennis by either, but just who would be more gutsy. I'm pretty sure Becker thought he had it in the bag in the 5th.
Seems to me, Edberg does better in 5 set matches on grass. Becker steamrolls very well. Edberg edges and comes back well against Becker usually.