It wasn't optional. I was forced to research it to get back to where I was before. It's effective right now, whatever the announcement says.
It was added and optional with the previous update - 1.16. With today's update - 1.17 - it became mandatory. There were two additional techs added with the update today that are
CURRENTLY optional - but which will become mandatory with the next update (usually in 2 weeks).
The release notes for both 1.16 and 1.17 clearly state which techs were added and when they will become mandatory.
From the update 1.16 release notes posted on
October 26th:
- Cerberus has moved from the Barracks to the Training Grounds, and is therefore no longer exclusively available to Humans, but also to Elves. For Elves, this new technology ('Training Grounds and Cerberus') is optional until the next update, for Humans it was already mandatory to research, but it did move position to an earlier chapter, which could cause the need to research it before you're able to continue in the research tree if you are at a specific point in the progress. It was impossible to make it optional for Humans too, since it would cause problems with the already released upgraded versions of Cerberus
From the update 1.17
- Both Humans and Elves get access to the Training Grounds levels 5-8 with a new technology in Chapter V. This technology will remain optional until the next update; due to this, the technology to research the first levels of the Training Grounds that was added in the previous update has now become mandatory to unlock for Elves (it already was for Humans)
- Elves will now have access to the Cerberus II, which can be unlocked in Chapter IV. This technology will remain optional until the next update.
What was added that is optional this update is the advanced research lvls 5-8 for the training grounds. The original tech that gives you the building was added
LAST update and became mandatory this update.
@innogames - maybe you should consider sending a message to all players when the release notes are posted prior to the update (with a direct link to the forum post) so they are forewarned about these kinds of changes.