color correction - Why do SLRs and DSLRs use different flash gels?

I occasionally use gels to match my flash to ambient lighting. It’s easy to find green gels (CTG) to match fluorescent lights and orange gels (CTO) to match incandescent. However, in my experience, the common gels provide too much coloration when shooting with DSLR. In particular, to match fluorescent, I usually need to shoot ½CTG, which is much harder to find than full CTG.

I have heard that the full CTG works well with film SLR, but something about the color sensitivity of DSLR means that they require ½CTG instead, and likewise for ½CTO. Is that correct? What’s the physical reason for it?