True, but the main use of Tin in Forestry (Bronze) is nerfed 50% by Gregtech (rightfully so, to match other Bronze recipe). RP doesn't use much Tin for the machines, but the alternate uses for it (Bucket etc) is once again nerfed by GregTech, so RP overall doesn't need much Tin. And it doesn't seem TE uses a lot of Tin, moreover it helps conserve it by enabling re-use of Cells and such via Liquid Transposer.
Meanwhile, IC2 needs quite a lot of it, especially at the start, but it seems to be sufficient by midgame. I still bumped the generation up a bit on my server, it can always be turned in to useful things, so I'd rather have extra later on than be shorthanded in the early game where it's really important.