I think the original message was that Sony changed from one OS to another OS, which resulted in a step backwards.

I'm just going to assume that they didn't know that the earlier devices were based upon Linux, because there wasn't much of a reason to know that they were based upon Linux. After all, Linux was behaving as an embedded OS in those earlier devices. I'm also going to assume that they interpreted Android as being Linux, because Android is based upon Linux. The bit about Linux providing the kernel and only a few open source projects providing the libraries isn't relevant to most people. The change between platforms is relevant to most people because the entire user interface had to be rewritten, and Sony may or may not have rewritten the support libraries.