While it is nice that it is a nice flush fit, it is not required. The reason for the reel clamp is to prevent the reel foot from bending underneath the reel. It creates stability. I have been on long range trips where a couple of the reels that were fishing did not have clamps. The YFT were running 200 to 290. 60 minute battles. Lots of drag. Over time, the reel foot started to bend up and it was not noticed. The next thing we knew, the reel slipped out from the reel seat as the foot started to bend up and become disengaged from the reel seat, and luckily the guy standing watching grabbed the reel before it when flying up the rod, stripping the guides as it went. The outfit was useless with the rod in one hand and the reel in someone else's hands, with the drag now backed off. Luckily Capt Mike on the Vagabond had a solution. He had an outfit with only a half a spool of line. He grabbed it, gave it to a deckhand with the line dangling. He had another deckhand grab the line with the fish on it, cut it and hang on with his hands with about 5 feet to work with. As the fish started working toward the bow, the gang of people were following Mike as he was attempting to splice the line before he got to the bow, walking very fast. Just as he got to the bow, the fish took off and Mike let the knot go. It held !! When the knot reappeared on the way up, it got trimmed so it would pass through the guides and he got the fish. The reel was junk as the foot was riveted in and bent to shit.
The other reel was a graphite framed Shimano LRS. Same thing, no reel clamp. So much upward pressure that the graphite cracked next to the reel foot and we almost lost that rig also. Same result, a quick splice and we got the fish.
If the reels just had the clamp from preventing the upward motion, there would have been no problem. The clamp does not have to be tightend like some people do with big wrenches. It just has to come in contact with the reel seat to prevent any upward movement and deformation of the reel seat.