Hi!

Good question, this puzzled me for a while as well, since I made this edit already months ago. But, as the summary says, this changeset removed footway tags on platforms, so these tags were copied from these two removed footways:
https://www.openstreetmap.org/way/479888653
https://www.openstreetmap.org/way/479888654

There they were added by user lordpake in this changeset:
https://www.openstreetmap.org/changeset/142644805