When using levitation over 127 to get the downwards effect, the players' motion nbt tag goes to a high positive value rather than negative. This remains and appears to tick down even after the levitation is removed.

In the attached image on the scoreboard on the right, the number next to 'TheKobinator' represents my in-game motion tag value. The one next to 'real' is my actual calculated motion in blocks per tick, both of which were scaled up by a factor of 1000.

In the image I was plummeting downwards extremely fast, yet my in-game motion was apparently over 1 block per tick upwards. This was after I'd just received levitation 128 for 2 ticks.

This raises issues for datapack creators if they are trying to detect motion for certain functions but are also using this levitation trick.