DS1 stopped falling asleep after every feed at 3 weeks (which I know is normal). But from then on he wouldnt fall asleep feeding at all. At about 10 weeks he started falling asleep feeding at bedtime, and it started working again for naps at 14 or 15 weeks.
Ive never come across it anywhere else, and I was wondering whether DS was odd, or whether I should expect DC2 (due in 5 weeks) to do something similar.
They're all different, what worked for your dc1 may not apply for your next bundle. I don't think the pattern you describe above is unusual, they go through stages and phases so what they do one week is the opposite of what they do this week. My ds is beside me having just fallen asleep after a feed, another time he could wail for a while just to keep me on my toes.