In Pro, if I search in My Content for GRSM% I get 98 items, although I can select 353:
When I search all Portal, I get 98 Items but can select 405. There's a few things that are owned by others that use my tag.
If I do different searches that "enable" the Find More Items", that's when the number of items returned is different than the number of items reported.
In AGOL, I get 697 Items (cuz' AGOL default search is going to show me SD files...Pro can't see those) BUT, notice how the default sort order (relevance?) is not the same as it is in Pro.
Arc returns the correct number of items (different # as arc won't show stuff in search results that it can't open, which is different from Pro):
Most importantly, I can't sort by popularity in Pro. Consider a new user whom has no idea what data to use in a new map. Can't go wrong the the Items that everyone else is using...and no, I'm not about to start pre-populating project maps with base layers in templates. If they want the layers, they'll add them. IT would have an aneurysm if they heard I was pre-populating web service layers in every single map (there goes the network).
My expectation is that default search order should be alphabetical or last modified date, or at least match the default as in AGOL. I have no explanation for where 98 is coming from, but it's misleading, and if I'm expecting a specific number of results from a search and all I'm going to get is 98 items reported despite what is listed in the search results......
In addition, Pro searching should present the same Portal search result sort options that Arc Map does. This can be easily accomplished by adding a right-click -> add column UI to the search results grid, which would present the user a choice of things to sort on and turn on/off things they don't want to see in search results (as most other software does).