Hi Zom,
Today I actually did run across a case where it is required to hold down CTRL and hit another key repeatedly (and quite quickly) as a keyboard control. That is in Flight Simulator II by Sublogic. This is remarkably sophisticated though the C64 graphics just can't do it justice. Because of the myriad of controls necessary to fly the airplane and adjust the instrumentation, the keyboard needs to be used quite extensively. This is documented here: FS2-ReferenceCard-C64.
For example, as you can see on the back side of the card, certain CTRL keys must be bashed repeatedly and very quickly to select which digits of the NAV radio, COM radio, ADF, or TRANSPONDER will be increased/decreased by subsequent presses on the > and < keys (actually the , and . keys as they are used unshifted). For example, holding CTRL and rapidly tapping T 3 times will cause > and < to increase/decrease the 3rd digit of the TRANSPONDER. But when the CTRL key only takes effect on the first key pressed while it is held down, tapping T 3 times selects the 1st digit and then sends the elevators down two increments; likewise, CTRL-NN, instead of selecting the NAV radio's lower digits, selects the high digits and then sends the flaps down one increment. A plane crash typically follows .
Also, the manual that you've included is actually the companion flight physics manual, and not the actual FS2 manual. The FS2 manual available via a cursory search of the internet is unfortunately marked up and scanned somewhat crookedly. I have a significantly cleaner copy (but with no fancy color cover, see below) I could scan and send you if you are interested.