Yes, you are right it works the same for both.
But with the setting I mentioned absThreshSS-BlocksConsolidation=-87dBm it means that only 1 beam is used to compare A3 for both source and target cell if RSRP of all beams is lower than -87 dBm.
So in weak RF all the rest of beams do not matter ,only teh strongest beam for source and target matters.
I mean measured beams by UE.
And if it is above -87 dBm things get complicated, because there could be 3-4 beams on source and 4-5 beams on taget cell fullfiling the criteria.
UE has to make the average for each serving and target cell, so it comes up with a single RSRP for serving cell and single RSRP of target cell and then compare for A3.