If it were me ... I would risk it and keep the tyre on and keep a real close eye on it, I've had a good run with both the plugs and goop (not in a road bike tyre though), I've had plugs last the full life of tyres on dirt bikes, quads, cars, 4x4's and trucks surely using both together must work out alright?
I would expect the "not for motorcycles" statement is just the manufacture covering their arse.

Had a flat on a snowy mountain ride on a jappa sports bike, repaired with plug & goop, did 1400kms @ wrong side of speed limit
did not have an issue until i pulled the tyre from the rim & the end of the bolt had damaged the sidewall.
if the rear deflates you still have control, i was doing 150+ when it went, no warning just a big weave going into the corner.
if its a front tyre then your face will meet the road real quick.

Another rocker owner said to me that the pressure repair pack type stuff has to be the right stuff. The rocka 5 spoke mags are expensive top shit metal and some pressure pack "fix a puncture" stuff can have a chemical reaction to the alloy,pitting and so on. Basically fucks your mega $ rim. I'd like to know anyones thoughts about that for my own sake.   Plugs and a pump are the go, but what about the liquid crap on certain type wheels?  

Your dead right there RT,couldn't have said it better myself. I did use the plug on my '84 (solid rear rim)in the states and got me out of a spot I was in so quick.