Of all the tests that are run on tbpl, mochitests are the last ones to receive manifests. As of this morning, we have landed all the changes that we can to have all our tests defined in mochitest.ini files and have removed the entries in b2g*.json, by putting entries in the appropriate mochitest.ini files.
Ahal, has done a good job of outlining what this means for b2g in his post. As mentioned there, this work was done by a dedicated community member :vaibhav1994 as he continues to write patches, investigate failures, and repeat until success.
For those interested in the next steps, we are looking forward to removing our build time filtering and start filtering tests at runtime. This work is being done by billm in bug 938019. Once that is landed we can start querying which tests are enabled/disabled per platform and track that over time!