Where did you see a reference to the 1509 encounter between Chinese and Portuguese in Malacca?

I suspect it has something to do with the Portuguese. Malacca is in modern day Malaysia, and the word for fork in Malay is Garpu, deriving from the Portuguese Garfo. While forks have been discovered in ancient Chinese tombs, they were typically not used by most people. I would suspect that either the Chinese traders adopted it from the Malaccans (who adopted it from the Portuguese) or alternatively it was known that the Portuguese ate with forks and thus as a courtesy supplied the guests with them.

It should also be noted that it was not at all unusual for people to use their own utensils-specifically knives, and in some cases it would be the same knife they would use for other purposes like skinning an animal or even combat.