I have always interpreted the +10 quite flexibly, as long as common-sense is applied (hey! - am I agreeing with 411A?
).
I would not propose the use of it on take-off around +10 because of the high temperatures of the bleed air. It really is no trouble, if pre-briefed, to put it on at any stage. From personal experience (737), a little care when putting it off is a bonus
Engines do not suddenly start icing-up like a Christmas cake at +9.99. I am also fairly certain they are unlikely to accumulate ice at 10.01.