Army Crawler

Hi, baby is 7 months + 1 week old. Started army crawling a month ago and uses alternate arm and leg movement (right leg was just hanging out at first, but he uses it almost constant now). He is very strong, sits independently, goes on all fours very often, plays in plank, bear crawl, and pulls himself to stand. I have been encouraging kneeling play, and crawling over my legs and pillows. But he still does not attempt to four point crawl, he will drop to his belly right away when he wants to move. I do not think that arm strength or endurance on hands and knees is an issue, as he holds this position for a while to play and will even balance on one hand at his cube toy. Should I be doing more or different things to encourage four point crawling? Is it a concern if he does not four point crawl? I have been stressing that I need to encourage more to get him crawling properly.