That all corresponds with common sense. However, as you know, BS7671 appears to say that 'isolation' does not require isolation of the neutral conductor in a TN system.Although the unswitched FCU only will isolate the line, not the neutral when the fuse is removed. So it depends on the level of "isolation" you require. For proper isolation all live conductors should be disconnected. That is the neutral as well as the line. Using the fuse to disconnect just the line is actually switching (like a light switch) and not isolation.
Kind Regards, John