JNC,
St. George's, Galt, Highland CC (in london), Kawartha and (original) Summit all have 5.
But other great works like Catarqui, Oshawa, Islington, Peterborough, (original) Cutten, Westmount, all have four.
He was not a prolific writer, so it is hard to get much of a sense of his desires for an ideal golf course. Most of the writing concern playability and (funny enough) maintenance issues.
To finally answer your question of did he look for five par 3's. I personally don't think so. I think it had more to do with the challenge of the terrain dictating an extra pr three to make the routing work.
Jasper, Banff, (especially) Capilano, Highlands, Montebello, and even to a degree St. george's are all on some pretty dramatic pieces of land. I think this is a bigger factor.
He definately tried to place the par threes on the most dramatic spot in the property, when he could. If you follow his great courses, this becomes a common theme, but like most architects the threes are sometimes the link between great land for longer holes.
#12 and 13 always struck me as the link between at Jasper for example
Westmount has one of his greatest collection of long holes (all are very good to excellent, but the threes are definately average at best. They feel like the links between great longer holes.
Highlands has no links, but that is because the routing follows the tillable land. He could not move soil like other jobs because the project only had one or two pieces of equipment (the rest was done by hand). That dictated his routing, and that is why it is one of his best.
May be the best ones to look at are his routings on very gentle land (specially if he had lots of land), to see what he choose to do.
As a funny note: 6 of the course I have listed have a pr three starting the back nine. That's an uncommonly large number too.