I'm sorry. I think I was not clear about this in my post above.

'Udolpho' is full of details of views from top of hills or cliffs as seen by not only Emily but also Blanche.

Catherine's ideas about what a painting of a landscape would look like is obviously developed from reading 'udolpho'.

But now the Tilneys talk about landscape from an entirely different perspective.

Ch 14
The Tilneys;
..appeared to contradict the very few notions she had entertained on the matter before. It seemed as if a good view were no longer to be taken from the top of an high hill, and that a clear blue sky was no longer a proof of a fine day...'

With this enlightenment;
"... when they gained the top of Beechen Cliff, she voluntarily rejected the whole city of Bath as unworthy to make part of a landscape."

Because it was from the top of a cliff, and because it included a *city*, whereas the Tilneys had spoken only of nature.
Remember in NA1 Eleanor rejects the temple as part of a proposed painting.

I agree, the walk is definitely a change from the Thorpes for Catherine.
Well, I do like Henry flaunting his wit. :-)