Striders can float
The bug
I was riding a strider on some lava, and a baby strider went underneath my mount, and then this happened. Even after removing the baby and getting back on dry land, they refused to stop flying. I believe this is caused by my next bug report, MC-176034.
Edit: As of 20w14a, striders can now float by simply walking off of a block it seems.
Video of Strider hit after been hit by a zoglin:
https://www.youtube.com/watch?v=ZT3Qo9eVF-E&feature=youtu.be