According to the Rama, the minimum is 1 hour, which you’ve never differentiated. According to Rashi, if you have meat in your teeth, it is assur to drink milk forever until you take out the meat. That is because the meat is considered real meat. Only according to the Rambam is the meat considered considered “batel” after 6 hours, but until then, there is no difference between eating them together or drinking the milk 2 hours after. I’m sure you can explain why it’s different than washing down your mouthful of steak with a cup of milk.
The Rambam does not hold that there’s a chashash of meat as you say, rather he holds it’s vadai meat. That would also helpfully explain the Rambam’s shitta of assuring dairy after chicken, as it would have certainly been a gezaira l’gzeira if there was no vadai chicken.
What may be pashut to you, only signals a lack of understanding of Siman 89.