They are supposed to be different plants, as their creator Triffid Park, markets them as 2 different entities. However, the fact that they came from the same creator could explain why they are so similar. It's possible the breeder selected 2 similar looking plants from the same batch of seedlings.
Less on history and theories, I've heard many growers say that the ‘Cross Teeth' variety displays the cilia overlapping very prominently, and is the main feature of the plant. 'Long Red Fingers' may once in a while take on the feature, but isn't known to cross its cilia as dramatically as 'Cross Teeth'. If you own both these plant, you can be assured they are different.
Back to a note on Triffid Park, the breeder at Triffid Park has proven to produce many similar plants under different names. For example, if you pay attention to the 'Fang' variety, which is from Triffid Park, it is very close in appearances to the 'Dingley Giant' variety, which is also a Triffid Park plant. The two plants are definitely different plants, but have similar characteristics. The same could be said about 'Clayton's Red Sunset' and 'Royal Red'.
Lastly, if you pay very close attention to the 'Crested Petiole' variety, you'll see once in a while it will exhibit traits reminiscent to both 'Cross Teeth' and 'Long Red Fingers'.