Not crawling

Anyone else have an 11 month old not yet crawling or is it just our sweetie? He lets us put him in the crawl position and sort of tries to move forward, but then either slides down onto his belly...or cries. He prefers to “butt scoot” as we call it (he actually gets anywhere he wants this way) or he can do an “army crawl” pretty well pulling himself forward with his arms/elbows. I’m not too worried because he is mobile and gets where he wants, but am a little concerned he doesn’t seem at all interested in getting in the “normal” crawl position. He also isn’t pulling up. If it matters, I walked on the later side...15-16 months.