So I discovered 2 things.
1) those joins with the tooltip error did not have a date joined. I will just have to make sure that they all do.
2) the 2nd tooltip ( below the date ) is in a title attribute:
Code:
<span data-cbtooltip-tooltip="04/29/2021 23:53:15" data-cbtooltip-width="" data-hascbtooltip="true" data-cbtooltip-position-my="bottom center" data-cbtooltip-position-at="top center" data-cbtooltip-classes="qtip-simple" data-hasqtip="3"><span class="cbDateTimeago" data-cbtimeago-datetime="2021-04-29T23:53:15-05:00" title="04/29/2021 23:53:16">6 months ago</span></span>
<span class="cbDateTimeago" data-cbtimeago-datetime="2021-04-29T23:53:15-05:00" title="04/29/2021 23:53:16">6 months ago</span>
I will hazard a guess the title comes from libraries/CBLib/CB/Legacy/LegacyComprofilerFunctions.php
I did check if switching back the default template changed anything. It doesn't.
It seems adding people to the groups from the backend is not setting the date. For now, I will have to fix their dates in the backend ( activity -> groupjive*joins )