It looks like particle toggle tracks use TimeRangeToNumberRange which gives the incorrect range as a result of CL 10893518 which fixed [Link Removed].
RESULT:
All particle systems deactivate when the sequence finishes.
EXPECTED:
The Fire_ParticleSystemEvaluationTest particle system would continue playing as the deactivate key is outside the playback range.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-95131 in the post.