But you really have to be careful levering a tubular - you can really stress the threads. The main benefit of leaving a glue gap at the rim joint is to provide a place to get removal started, using your thumbs.

Sometimes I use a sharp knife to weaken the glue seam by cutting it gently as I shove the tire with my thumb. It's a good trick when my thumbs have had it.

First, last, and always, do no harm! Your safety on the road depends on those little tiny threads!