I ran into a similar issue. Parked in a garage about 3 levels below ground with no cell service last night. TeslaFi showed my drive there and back as one LONG drive with hours of offline data in the middle, rather than two separate drives because the end point of the first drive had no cell coverage. The drive record shows 19.5% accuracy.
@Jdeck, was this something you were still tinkering with? The only relevant bugs I could find were
0000022: Catch "offline" status better. - TeslaFi Bug Tracker with a few linked bugs that had been closed out and
0000094: Explore Adding New Statuses Not Currently Documented - TeslaFi Bug Tracker that I opened about adding new statuses for better clarity. Perhaps with the new merging function, Issue 94 could be implemented with a split function to better manipulate the data?