Seems to have worked, the bug just got upgraded from P3 priority to P1 (the second highest priority).
Per Google, a P1 bug is defined as follows:
"An issue that needs to be addressed quickly. Such an issue significantly impacts a large percentage of users; if there is a workaround it is partial or overly painful. The impact of the issue is to a core organizational function, or fundamentally impedes another team."
I haven't actually seen my phone use B41 though, it just idles on it. As soon as I start an active data session, it switches back to n41 + B2/66. It's almost like the network is offloading idle phones onto B41.
Knowing that they have Carrier aggregation active with B-41 now, T-Mobile may have changed thresholds on what the level has to be for your phone to attempt to use Band 41. With aggregation, the range and usability of Band 41 increases.