While I cannot understand the video language, the title suggests he is referring to two early destroyers (Type 051G) decommissioned in 2020. These basically have no real air defence capabilities to speak of, and little capabilities in general - not even a helicopter hangar. If you are referring to these ships, they certainly don't have the S-300 onboard. There's no capability-minded reasons for Pakistan to buy them, especially as metal fatigue will already be high given how long they have been around.
The only Chinese destroyers using the S-300FM are the two Type 051C ships, and these still have a fair deal of service life left, being commissioned in the early 2000s. They could well be sold to friendly countries before retiring from PLAN, however. There's no evidence they can use the YJ-21, and I don't believe they can. The modern PLAN destroyers that can use the YJ-21 have deeper VLS cells, compared to other PLAN and even western destroyers.