What does "not mind pruning" mean, specifically, in this instance?

Since I am planting it close to the property line, the side of the tree that grows towards my neighbor will be at the mercy of that neighbor and his clippers.

Above 7 feet, it has plenty of room to grow east, west, north and straight up-although growing north would be over the top of the flat black asphalt of the carport roof.

Enkianthus campanulatus would probably be about right, there is a bank in Lynnwood that has several in nooks on the south side of the building. However, you are not going to find this at a nursery already 7 feet tall. And something that is comparatively easily and affordably acquired 7 feet tall is likely to be too vigorous for a space 4 feet wide. You may have to try something comparatively slow and restrained (like Enkianthus campanulatus) and just be content to wait for it to grow as tall as you want. Or put up a trellis.

I found a 6 foot apple serviceberry, for $60. It's supposed to grow to 20 to 25 feet. Even if it is too vigorous, in that range it seems controllable. I saw a mention of it being prunable into a large shrub.

I don't know if Enkianthus campanulatus is going to get tall enough for my purposes.

Well I went with my strong lean and bought a serviceberry-amelanchier grandiflora autumn brilliance. Wells Medina had an 11 footer whose shape I liked. Hopefully it didn't mind the ride across 520 in my pickup too much.