The following issues were observed using a logic analyzer. Version 2.8p15 is used.
When reading the device power status OWFS sometimes reads the status, but is often only addresses the device, and often does nothing on the bus, it probably reads the value from a status structure. In practice the recognized power status of a newly attached device does not match the actual status. This is causing temperature conversions on un-powered devices with pooling instead of active pullup.