Profile pictures in activity stream update when user changes profile picture, but revert to old picture when screen is refreshed

A while back there was a change that gave profile pictures a different URL each time it was updated, therefore activity streams contain older versions of images.

A change was recently made that fixed the issue with profile pictures not being updated live on the UI in the activity stream.

Now what happens is that when you change your profile picture, the updated picture is put in the activity stream, them when the user refreshes the page the pictures revert to the old one.

Somehow I think we knew and accepted this would be a side-effect of making the profile picture URL different, so I'm not sure we need to fix the issue of showing the older profile image the activity stream, as opposed to just make it so that profile picture updates don't update the activity stream automatically.
Is there any reason this is optional here, but not in the other methods?