I argued so much with DS about the need to revise from mid-January to the end of february (when he finally started), that I genuinely got sick of the sound of my voice.
IME, they can want the results and intend to do enough work to get them, but they will look at the DC around them at school and if they lie say that they aren't revising in evenings and at weekends, then your DC will be liable to think you are being OTT about it.
At least this time, I'll have DS1 to back me up and tell DS2 that some people say they aren't working and then it turns out that they have been since October.