to anyone who may need it:
tumblr mobile can automatically pause all gifs on your dash, no not just on data saving mode
go to your account page, click settings, then general settings.
scroll down until you see experiments, and click on labs. The tumblr labs image flashes around a bit so be aware of that
under that screen turn on “Tumblr Labs,” then “Tap To Play Gifs”
this is on an Android, so if someone with apple could check that’d be really helpful!