Portfolio is interesting in a diabolical way. Legacy owners feel its presence since we no longer have access to the pre-2017 unsold inventory that was burning a hole in the Developer's product. But strictly speaking, whether it was sold to Hyatt Portfolio or to an individual, we never had any right to it anyway - it was just a nice bonus while it lasted.
But with the annual conversion, their modest program has attracted at least six or seven thousand legacy "hybrid" owners who give up their unit-weeks to the Portfolio on an annual basis. Those folks then reduce our trading pool even more.
And over time, like you said - trading on legacy alone will get more challenging as more hybrid owners sign up.