RC is not really a big industry. And makers of LiPo packs have to use industry standard LiPo single cells. If you look at RC airplanes you can get very small to very big packs. But once you get up to a usable mAh rate for cars the packs need to be a certain dimension.
Surely Trakpower made the smaller 3200 saddle packs in order to make fitting easier, as the 4800 ones are a bit big. If you need anything smaller than that the mAh rating will again need to be smaller... and you'll then have runtime problems - and also loose the fantastic feature of long practise runtimes with LiPo. Not to forget the weight is low per se so you'd rather carry a larger battery. Lead weight does not give extra runtime
And as long as it's not a competitive advantage why should EFRA bother for 1:10 OR?