I believe this is just best practice being enforced by the version of the GWTP plugin you are using. It looks like you are using the old version of the plugin (for before GWTP 1.0)...
The new plugin allows capitals in the names:
Anyhow I would say use capitals if you want to, as long as it works.
More importantly, get using the current versions of GWTP and the associated plugin: https://github.com/ArcBees/gwtp-eclipse-plugin