Hi @fiammdin ,
What we would expect in the calendar of UserB, is the new time proposal window to be booked free, or with new attribute: "temporary blocked" and marked. But that is not the case.
Agree with Andy that this is actually a by design behavior that the new proposed time won't be blocked until accecpted by the meeting organizer. And currently, if you would like the new proposed time range to be temporarily blocked, you may have to manually create an event and specify a status like Tentative.
Then regarding the "Suggest a Feature" button, according to the "Notes" in this document, the latest version of your Office products is required to send feedback using the best and most up-to-date experience. Therefore chances are that the different user interface you shared above might be related to the build of the Outlook client.
I just checked in my Outlook for Microsoft 365(Version 2019, Build 14430.20306, Current Channel) and can see the "Suggest a Feature" at my end, so I've sumbitted this feature based on your description:
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