John de la Pole, 2nd Duke of Suffolk - Grace Catherine De La Pole

If you mean random personal trees on sites where we test our DNA, use heaping amounts of caution. People can say anything, as you've already sorted out, and once that happens, particularly on Ancestry with their "hints", it takes off as people blindly accept as fact.

Medlands, The Peerage, University websites, original church records, those are the places to go. Ancestry and so on is fine for HINTS.

From the Peerage,

https://thepeerage.com/p10758.htm#i107578

Katherine de la Pole was born before 1491. She was the daughter of John de la Pole, 2nd Duke of Suffolk and Elizabeth Plantagenet.1 She married William Stourton, 5th Baron Stourton, son of William Stourton, 2nd Baron Stourton and Margaret Chideocke.1
Her married name became Stourton.1

Likewise, if you see something on Wikipedia, WikiTree or HERE, is it sourced? If so, look at the source(s).

Medlands seems to be down at the moment, so I cannot give you the specific link(s). You can see more about it in a general sense here, just a summary of what it is:https://www.wikitree.com/wiki/Space:Medieval_Lands