What about thiese examples?
Search params: have* * known* that
Managing the national curriculum. ed. Brighouse, Tim and Moon, Bob. Harlow: Longman Group UK Ltd, 1991, pp. 27-129. 1639 s-units.
By definition, many thirteen-year-olds in secondary schools will be achieving at the level of many sixteen-year-olds. In theory, we
have always known that.
Living magically: a new vision of reality. Edwards, Gill. London: Judy Piatkus (Pubs) Ltd, 1991, pp. 45-160. 2798 s-units.
Mystics have always known that we create our own reality.
Do these examples correctly illustrate the situation? I understand that in BNC one can find anything. But the first example is by Longman.
And.
Please, have a look here:
https://www.oxfordlearnersdictionaries.com/definition/english/know_1?q=know
I'd like to draw your attention to the phrase that this word is "not used in the progressive tenses". If it were not used in a perfect tense, they would state that.
So, the question is: does any textbook or a dictionary state that this word is not used in perfect tenses?
Or do these examples illustrate cases 10, 11 (experience) in the article?
But anyway case 1 (have information) doesn't prevent us from using perfect tenses.