Eh?
"Citrix has not previously set the expectation that such customers could be denied maintenance. Indeed the very word 'perpetual' more or less implies the opposite".
"Perpetual" doesn't imply ongoing maintenance at all.
It simply means that you pay once and the license never expires. So as long as you have a platform that supports it, it will (or should*) keep working without having to pay any more money. It does NOT mean that you will continue to get updates and security fixes for it.
*There is an exception to this. Zemax OpticStudio "perpetual" licenses (prior to their aquisition to Ansys) require the perpetual license be assigned to a My Zemax user ID on their My Zemax portal. Shutdown the portal and your "so-called perpetual" license becomes useless.
Rather like all those devices which won't work without a subscription (free or paid) on the manufacture's "cloud" system. Shutdown that and all that shiny hardware becomes scrap.