It seems fishy to me too, lol.
I am only quoting the guy at the RCA help line. It could be that my bargain LED/DVD TV has a poor tuner but the RCA guy told me that even the high end TVs sometimes have trouble pulling in channels.
I was thinking that in the past I had read that any of the tuners don't need a full 90+% signal to have a good picture but I could be wrong on that. I have Zenith converter boxes and they had a very good rating when they were new and have worked great for several years. My converters sure got by with a 65 to 90% signal.
Maybe the TV manufactures have been slacking off on tuner performance since so many of them are hooked to cable. This seems to be true of the reviews on the speakers on the newer TVs as they want to sell you surround sound or at least a sound bar. My picture is excellent but the speakers are embarrassingly bad and "tinny" even compared to the small 20 year old Quasar it is replacing. They are passable at best after using the equalizer function to tune them.