Last time I saw that type of seatpost was on a pair of bikes for a pair of young lads purchased by their parents in 1971, on way too big Schwinn Supersports. Was done to get the reach reduced and saddle a bit lower.

My Mom happened to see them and stated it must be to prevent grandchildren when they crunched the top tube.

so, a Schwinn dealer bigger the bike, bigger the man part exchange.

the two lads were tall but not huge bike tall.