Adding to @mykepredko: This functionality is far from the needed precision for a z-axis. Also, z-axes often exert high forces over very short distances (depending on gearing and drive system).
Looking at the Manta’s schematic, it even seems that they wired the connectors in parallel. This is very unlikely to ever work with stallguard and is, well, pretty dumb. See 7. Wiring Stepper Motors in Series or Parallel