It's clear from the existing tests that the different keys were intentional, but there are a couple of good reasons to normalize them:

1. It makes it a lot easier to automate the process of pre-loading an engine into the requires object (you don't have to keep track of the alternate key names)
2. The current scheme is not consistent--Liquid loads the "tinyliquid" engine but uses "requires.liquid", and Hogan loads the "hogan.js" engine but uses "requires.hogan"