What's with the single lane bus lanes on the IndyGO BRT system?

It's just something that I've noticed when reading up on some of the interesting BRT work going on in Indianapolis.

I appreciate that, unlike most "BRT" systems in the USA, they have center-running bus lanes and other real BRT features, but I couldn't help but notice some of these sections where there's only one BRT lane that I assume is shared by buses in both directions.

What exactly is the use case for such road configurations, and is there any reason why IndyGO could not have two bus lanes running in both directions? I assume it would make the system more reliable and efficient overall.