Ignore the box around the text as I found the image on Reddit the other day but George said this very thing in Paul Duncan’s Original Trilogy book. Darth Vader/Anakin in the instance with Luke and even Qui-Gon when he told Shimi how unusually strong the Force is with Anakin didn’t realise how attuned they were as Midi-Chlorians are microscopic lifeforms and not the Force. It’s not until Qui-Gon took Anakin’s blood sample did he come to the conclusion that he must be the Chosen One.