I suspect that's the case. There is something a little odd about the design about the Canon 70-300L, though. For example, if you compare it to the Canon 70-200/2.8L IS II, both have the same specified MFD and maximum magnification (47.2" and 0.21x), but obviously the 70-300mm has a 50% longer focal length at the long end. Canon mentioned a The Tamron 70-300 VC, despite not being able to focus as close (55.1" MFD) achieves a higher 0.25x maximum magnification.
The 70-300 L has a 'floating' optical system (the 85L II has this, too). Canon stated, "As mentioned above, the use of a “floating” optical system means that as the lens is progressively focused closer, other lens elements continually change position to preserve image quality throughout the focus range. (Many lenses are optimized for best quality at or near infinity, and as focused closer, there’s a drop-off in contrast and sharpness… that’s not the case with this new lens)." It seems something had to be traded for that sharpness when focusing close, and that something translates to maximum magnification, apparent focal length, or FoV at the long end (three ways of saying the same thing, sort of).