According to the information I was given and reading the older Hotpoint manuals, I was always under the impression that the OOB control was acheived by the electronics sensing the motor speed variance that occurs when an OOB load is lifted up to the top of the drum, then dropped down the other side. No mention of the belt slipping having anything to do with the process is mentioned in any Hotpoint manual that I can see.
Might be worth adding a note regarding ‘conductive’ belts, as used in many instances these days, number on belt usually has the letter E as part of the belt ID number. Essential to disperse static.