I made an effort to watch the defensive end closely last night as well. As you mentioned, what Gabe does is not "flashy", but he really does a great job staying in front of his man, limiting their scoring chances, and especially working over screens. He's very quick to get through and back on his man which protects our bigs. His "help" defense is what stood out for me. On one play in particular, he slid across on help and created a turnover. Both was there to get the loose ball and the "steal" on the stat sheet, but it was clear Gabe's help side D created the turnover.
My general thought is that being a "Great / Elite Defender" is based upon reputation. You really can't see it on a stat sheet. As you mentioned, our coaches love what he brings to the defensive end and I'm sure it's noticed by the coaching staffs of our opponents as well. A lot of guys "look the part" when it comes to defense, but don't get it done because of the level of effort and fight truly involved.