On mine, the coating eliminates the metallic click but the minute play is mostly still there.
It's odd... only the first one, Black/Black, has the vert. play. It's the frame itself I believe.
The Silver/Black is fine and both Black covers click on the first frame.
I just tried the cover from the new Black/Blue on the first... as described above.
Sorry I can't say it'll fix the play, but as you say (I agree) it's not a major annoyance.
I actually have to use a two-handed hold to make mine click. It's under a half mil of play.
If it matters...
Black/Black - #406X <- this is the "clicky" one
Silver/Black - #1032X
Black/Blue - #907X
"Mr. Clicky" (I think I'll keep that

) is also the one with the dodgy 510.
My 'Mizer and a slew of other attys wont sit flush.