DAU has always taught that orders under IDIQ contracts are not stand alone contracts. What has changed in the FAR or DFARS to now have DCMA instruct their GPA's to manage property under IDIQ orders which are not contracts? Isn't property required to be accountable to a contract? Have you changed your course material?
You actually answered your own question. TOs ARE contracts but they are not "stand alone contracts". This means a PCO cannot issue a task order (or D.O.) that is not associated with an overarching IDIQ contract. If you were to examine an IDIQ you would notice that there is no funding on the IDIQ. Only a guaranteed minimum. The guaranteed minimum is necessary to meet the basic legal requirements of a Govt contract...which are Offer, Acceptance, Consideration (money), Mutual Assent, and Legal Authority to Bind the Govt. So the Govt guarantees a minimum to fulfill the consideration aspect of contract law. But this also means we, the Govt, can issue an IDIQ and then NEVER issue a task order. Whether Single Award or Multiple Award.
Perhaps the mechanics of an IDIQ and TO might provide insight. The IDIQ is the contract vehicle that is offered under Full and Open Competition (typically) satisfying CICA. The IDIQ procurement is subject to all of the protest rules. In the IDIQ all of the general terms and conditions of the contract are spelled out, including pricing...and may include the use of property, but not usually. Property is usually handled at the TO level because TOs are unique to each requiring activity. The IDIQ terms and conditions flow down to any TO written off the IDIQ. Typically, IDIQs have ceiling prices, ordering periods, and run several years. Once an IDIQ is in place, PCOs send out Request for Task Order Proposals (RTOPS, much like an RFP). The RTOP includes a PWS. It is within the PWS, typically paragraphs 3 and 4, where property is addressed. If it is a single award IDIQ, then the RTOP only goes to the one contractor. If it is a multiple award IDIQ the RTOP goes to all members of the IDIQ pool (those who competed at the IDIQ level and were awarded an IDIQ contract). Let's say there were 4 contractors in the IDIQ pool. Each contractor now competes for the TO under "fair opportunity" rules...not full and open. Full and open was satisfied at the IDIQ level. Fair Opportunity also restricts protest rights...which is an advantage to TOs. Once the proposal(s) is/are received, negotiations occur, and the details of the TO are finalized and it is executed. The TO is funded and performance begins. If a contractor fails to perform on a TO they can be held in breech, T for D'd, and T for C'd. If a contractor's task order is terminated, the IDIQ still remains. So, as you can see, a task order IS a contract. An IDIQ is a stand alone contract and is not dependent on any other vehicle. A TO is a contract but is dependent on an overarching IDIQ and not stand alone.
A further point is FAR 16.504(c)(1)(ii)(D)(1), which states in part "no task or delivery order contract in an amount to exceed $112 million (including all options) may be awarded to a single source, unless..." So here, the FAR even calls a task order a contract.