Most requirements like this are set by insurance companies, not the CFI.
Personally, I'm a little sceptical about this. Certainly different policies have different conditions, but often flying schools tend to avoid arguments by hiding behind non-existent insurance requirements ("I'm sorry, but our hands are tied ..."). Might not be the case here, I don't know.
What really galls me is when a school claims that its insurance requires that renters maintain currency by flying the school's airplanes every 30 days (or 45 days, or whatever).
This is just silly: no underwriter cares whether you fly the school's particular airplanes, they just want to ensure that you are current on type (a 152 is a 152 is a 152).