I don't know if it's part of a larger trend, but I seem to see 1. ... f5 after I play d4 quite often lately on the site here.
1. d4 players take note!
EDIT: It reminded me of a game I studied from when I first started playing competitively.
One of my very first chess books was Informant 42. It was like the Da Vinci Code for me. The game below was in it.
I had a friend at my college club who was better than me (everyone was...), and he played the Dutch, so my study naturally gravitated to this game, which still sticks in my mind 25+ years later: