You’re obfuscating the point being made, i.e. that you just can’t spout Det. 18 as some hard and fast rule, when you have no clue if God Himself set a undeclared (by the prophet) condition that would make the word not come to pass.
In Jeremiah 18, God explicitly says He may tell a prophet to declare something, and then He may change his mind on what was declared.
True, but Isaiah 38:1-5 does not contradict Deuteronomy 18:22.
And there are several false prophets listed in Jeremiah, receiving rather gruesome punishments for their presumptuousness.