You can get low THC/high CBD ratios in any format. In Switzerland for example, products with CBD is legal, and up to 1% of THC. So you end up with lots of different products, including dry herb, that has 0-1% THC.

It may be harder to get in places where higher THC content is legal (since most users want more THC), but it's definitely not limited to just wet cartridges.

You COULD get much higher ratios of CBD and THC in this format if the product is not chopped to hell in back. The issue with black market carts is that it is hard to tell whether it is the genuine article with a visual inspection or by tasting the product. It's much easier with the actual flower. In theory the liquid is more potent, in practice without regulation not so much

You can buy high-CBD flower though.