This is an interesting example of what can perhaps best be described as deluded pedantry. Google “does muscle weigh more than fat”, and you’ll find a variety of sources telling you that it doesn’t. As one of them puts it:
Muscle doesn’t weigh more than fat. A pound of muscle weighs the same as a pound of fat. Muscle is more dense than fat though, so a pound of muscle takes up less space than a pound of fat.
In other words, every substance in the universe weighs the same as every other substance. Just to clear this up: when people ask if muscle weighs more than fat, they’re asking if an equal volume of muscle and fat have the same weight. Which I would have thought was obvious.