"Continuously variable for FM doesn't make sense."

Maybe not, but...

In the old days there were stations that sounded better when off tuned, and I mean with the dual tuning meters. This can only be because the multipath was at the edge of the IF bandwidth and mistuning took it out of the passband. If so, the simple loss of the harmonics obviously caused less distortion than the multipath would.

Luxman believed it and had a ine for a few years that actually detected multipath and would actually mistune a station for lowest distortion based on the multipath measurement obviously.

Thus, even better would be variable control of both the upper and lower sidebands. this would allow you to tune in the center of the detector range and do what the Luxman did, or what mistuning did a long time ago. Adjusting it manually would be a different story of course, few people could figure it out.

However being in the center of the detector range is simply not important now that they usually have a much wider range than the IF bandwidth. The Luxman engineers probably figured that is would be pretty rare for the multipath to happen at both sidebands and figured that the easiest way to do it would be mistuning.

I have seen such a tuner in action. It would tune of course, then it went into the test type mode and you could see the tuning indicator change and there was another small indicator on there that I think indicated the detected multipath.

That was actually one of the best mix/match systems I heard. The Luxman was a receiver and fed a pair of ADS which had blown tweeters. The other amp fed a Bose Acoustimass system with the satellites right on top of the ADS'. And I could not get it to clip. I shook the floor pretty good, and the house was built on a slab. Longwood, Florida, every house is on a slab unless you are filthy rich and want to waste money. Certain times of the year if you stand in one spot out in the yard you start sinking, that is if the fire ants don't get to you and make you go in. Of course there was also the alligator in the swamp next door...

Anyway, I think DXing anything is not what it once was. All the digital garbage on the signal, you limit the IF bandwidth that is sure to cause some distortion. And even some of the best old tuners need a modification just to handle the signal without spurting a bunch of noise into it. As far as DXing TV which I used to do, that is over period. It seems like they don't want us watching things that are not meant for the area. Like Canadian news I used to watch on CFPL, channel 10. Now we have the internet and they are having a hard time stopping that. Ever look at RT ? Sure they are biased, but they are not off the wall. Even PressTV, biased ? Sure, but CNN ain't ? Bull****.

And BTW, you can get most FM in the country on iheartradio.com I think, though it may have limitations applied. Like youtube "this video is not available in your country". But there are programs that can spoof your location. Consider them the new DX antennae.