Need some help understanding what UA is going to do with me when I arrive at the airport to checkin.

Background. Flying USA-BRU-EBB next week. EBB requires negative PCR test 72 hours prior to first flight departure (so noon on Sunday at the earliest). BRU says online no PCR test required if transiting, but UA travel ready center (and twitter agents) say that have to have a test no more than 72 hours old from when you arrive in BRU (so midnight Sunday at the earliest). According to Belgium and Brussels websites, that's not correct and no test needed for transit. Would prefer to get the test Sunday afternoon since the turnaround time is taking so long now, but don't want to get told "no" at checkin by United (even though the information they have is incorrect). Recommendations?