I do not think this is true. IDBs trigger a mandatory report to the DOT and statutory compensation based on 14 CFR § 250.5, which I can assure you is substantially more than the typical VDB offering. Invol'd customers need to sign a form outlining their rights and nature of compensation offered and then the hard copy of the form and complete oversale report must be retained at the station for a period of over one year from the date of travel. No small matter.

The legacy CO automated oversale manager (OVS, built into SHARES) is actually a pretty good tool for processing oversale situations. Perhaps a lack of training would have prompted some overworked agents in the early phases of PSS cutover to IDB pax before soliciting volunteers, but this is decidedly against UAL policy.

On the other hand, I have heard of situations where passengers who were actually invol'd were given compensation and reaccomodated as if they were VDB pax, avoiding the mandatory reporting procedures and statutory compensation. Personally, I find the latter scenario more reprehensible.