On the point of Patrick's awareness of the changes, I wonder if some of this wasn't present in embryonic and slightly inchoate form in The Thuggery Affair, in which Patrick tells the others in the priest-hole about his infant misunderstanding that they were still living in Penal Times (I think he's supposed to be about 6 when he was labouring under that misconception). TTA was published in 1964, so predates the people-noticing-changes watershed, but presumably as a well-informed convert Forest was more alert than most to what was going on. And it does provide some in-universe plausibility for Patrick's precious precocity.