Very odd English

In the page linked below, first line reads:
> Json.NET should be used for serialization and deserialization. Provides serialization and deserialization functionality for AJAX-enabled applications.

The wording and punctuation is very odd. It reads like an ad.

Where did this line come from? There is no reason mentioned on why Microsoft would recommend a 3rd party solution over their own.

https://docs.microsoft.com/en-us/dotnet/api/system.web.script.serialization.javascriptserializer