-B ignored?

I'm having converting a 3 GB geojson of OSM data:

tippecanoe/tippecanoe -l osmhighway -f -o osmroads.mbtiles -ac -ar -ao -Z 5 -z 17 -P -B 14 osmroads.geojson
osmroads.geojson:348753: Found ] at top level
osmroads.geojson:350201: Reached EOF without all containers being closed
Sorting 1435380 features
1435380 features, 110358784 bytes of geometry, 32565389 bytes of metadata, 23581670 bytes of string pool
tile 5/29/18 size is 2200531 with detail 12, >500000
tile 5/26/19 size is 1223582 with detail 12, >500000
tile 5/28/19 has 255118 features, >200000
Try using -B to set a higher base zoom level.
tile 5/26/19 size is 885916 with detail 11, >500000
tile 5/29/19 size is 3181219 with detail 12, >500000
tile 5/26/19 size is 600371 with detail 10, >500000
tile 5/29/18 size is 1588578 with detail 11, >500000
tile 5/29/18 size is 1083596 with detail 10, >500000
tile 5/29/18 size is 711200 with detail 9, >500000
tile 5/29/19 size is 2305194 with detail 11, >500000
tile 5/29/19 size is 1581186 with detail 10, >500000
tile 5/26/18 size is 615977 with detail 12, >500000
tile 5/29/19 size is 1038138 with detail 9, >500000
tile 5/29/19 size is 662081 with detail 8, >500000
tile 5/31/19 size is 1180098 with detail 12, >500000
tile 5/31/19 size is 872921 with detail 11, >500000
tile 5/31/19 size is 611766 with detail 10, >500000
  32.1%  5/29/13


*** NOTE TILES ONLY COMPLETE THROUGH ZOOM 4 ***

Regardless what number I pass to -B, it bails at 32.1%. Even -B 18. Am I doing something wrong?

Reproduce the issue with the command shown and compare runs using different -B values, including -B 18. Start at the tippecanoe CLI option handling and follow how the base zoom affects oversized tiles and the completion limit. Done means explaining why processing still stops at the reported zoom and adding a regression test if the behavior is incorrect.