Tell me something I don't know.

It SAYS that, but regardless of the source, don't believe everything you read on the internet.

Will and would are both modal auxiliary verbs, and as such, don't actually have a past tense in the sense other verbs do. They don't have participles either. You don't have "woulding" or "woulded", and neither has a present or past tense either. Even if you wanted to argue it, what's the past tense of other modal auxiliaries? What's the past tense of "may"? Or "should"? And before you say "May have" or "should have", then why isn't the past tense of "will" "will have?"

The same is true of "can" and "could". Could is NOT the past tense of "can" because a past tense for a modal auxiliary verb is nonsensical. What they MEAN when they write that is "could is a verb that can be used in place of can in some situations to refer to the ability to do something having taken place in the past", but they are different words that happen to share related usage.

In the case of "will"/"would", not even THIS makes sense. Will is used as an indicator to shift the following verb's action into the future. The past tense of shifting something into the future means... what? Making something hypothetical?

While calling these verbs "past tense" is a functional shorthand for explaining their function, the reality is modal auxiliaries do not have tenses or other forms, and it's disappointing to see the British council screw this up.