Minecart is pushed off the rail when pushed by a piston

So, I was testing the current TNT duplication method, trying to create it myself without following a setp-by-step guide, and pushed a minecart on a rail. To my surprise, it was popped off of the rail!

 

NOTE: The rail was on a slime block with a slime block in the direction of push.

 

I do however wonder if this may possibly be a feature in 1.15, as I have not tested it with the Honey Block yet.