To me, we spend such a lot of time ensuring a 'perfect' glue job. We fret and fuss about the preparation of the rim, the choice of glue, gluing technique, etc. We know that several days is required to get the best result. The purpose of all of this is to ensure the maximum bond strength for racing. Why would we do that, then leave a built-in weak spot in that 'perfect' glue job.
First of all, "a weak spot" is a no different than adding a few spoke holes to a rim. I mean you can't possibly glue those in any way to not make them a weak spot, right?
Either way the choice is for you to have: it's either taking a risk no bigger than me winning the lottery by introducing a point where the tubular can be lifted off the rim or a few more minutes fussing at the side of a road before you can swing that prepped spare on.
As for the higher rolling resistance: a badly glued tubular will exhibit a little higher rolling resistance. Same for overly thick cement. But a 1/2 inch or even less ? I'd be surprised if it were even measurable.
If it is then wheels with fewer spokes should also have lower rolling resistance. Maybe they do, no one's ever measured that AFAIK.
P.S. Still hate mounting these Conti Comps.......