If the plug will expand enought to grip the steerer it will work fine.

For my first threadless fork installation I bought a Kestrel EMS Pro with a Cr-mo steerer. Since I wasn't sure how long to leave the steerer until I tried the bike a few times, I put in a lot of spacers and used a compression plug. After I got the bar height dialed in and cut the steerer to final length, I replace the plug with a star nut but the plug would have served as a permanant adjuster too.