I don’t see it that way. It’s a quick glance to cross-check the 100KT call against another another certified IAS instrument, and then if this is good, a gross error check against an entirely different source. Can be done in about 1-2 seconds…
If the PM is doing his job on the Airbus, all airspeed indications are scanned during the roll even during the low speed regime (a slight reference to this is made in the FCTM) possibly enabling a discrepancy to be identified early and a reject safely made during the low speed regime. As PF and PIC I can’t control if the PM has done this or not, hence the 100 knot call is the last chance I have to know if we have a discrepancy. But now we are in the high speed regime and quickly approaching V1 (in some instances) - hence it’s not written procedure to reject - it’s now a command decision.
My responses to you will end here. I just don’t agree with some non-published (for good reason) techniques made by instructors that are then adopted by trainees as gospel - their technique may not fit your situation / context, and could lead to a negative outcome, especially as no formal risk analysis has been performed and you won’t have any leg to stand on should you need to reference it in a court of law (or the chief pilots office).