I just tried a HK55 (500459 32 tooth blade)blade on my TS55 and had no issues.
I was a little concerned about the riving knife, but as it will travel independently of the blade and should ride along the top of the board if the kerf is too small, I figured what the he!!, however, it was able to deploy fully in to the narrower kerf without any problem.
I ended up with a clean cut and never saw any impact on my rail splinter guard, all in all I can't figure (yet) why they say it should not be used on the TS55? [unsure]