Not the author but I grew up using this tech and I recall it being seconds rather than minutes.

There must have been some TVs with a page cache? (Not that I ever saw one, admittedly).

Yes, they where. But you needed to wait to get all the pages, which wasn't a fast procedure. Around a minute or such, I can't remember.

It depended on the page. Clearly to have a complete cache you'd have to wait for everything to have come around, but common pages like contents or news headlines were transmitted more often than the others, so they entered the Fasttext cache more quickly.

It would have to be on and tuned into the right channel in the first place in order to build a cache.