xpabu,
You bring up an important point, because Oracle sales frequently attempt to increase revenue in this fashion, by questioning how constrained VMs work.
In the cited paragraph, words matter. The relevant sentence reads...
For the purposes of licensing Oracle programs in an Authorized Cloud Environment, customers are required to count the maximum available vCPUs of an instance type...
Please note the highlighted word available? By any definition, available means able to be used. As Kellyn pointed out previously, additional vCPUs allocated to a constrained VM are not able to be used, and therefore are not available. Allocated and available are not the same thing, and that should be the end of discussion.
However, it should be expected for Oracle to attempt additional word contortions, but the base concept enabled versus disabled CPUs is one that Oracle simply cannot fight successfully, when informed people of good intent are involved.
So, an important word of advice: do not engage in lengthy argument with the sales teams at Oracle, as they have an obvious personal vested interest in the count of CPU cores. Instead, demand to be connected with Oracle's License Management Services (LMS) team, which is the team responsible to regulatory agencies for the proper licensing of customers, and work directly with them. Requesting involvement by Oracle LMS is a signal to the sales teams that their game is over. They do not want customers talking directly with LMS. This is why there is a Contact LMS button right on the LMS home page.