To allow this ruleset to still be used by projects supporting older WP versions as well as newer WP versions, they will - for now - not be removed from the ruleset.
However, documenting what WP version introduced certain polyfills and where applicable in what version of WP they were removed, seems prudent.
Note: the JSON related polyfills will most likely also be removed in WP 5.3, but those changes haven't been committed yet.
WP 5.3 will drop a number of polyfills.
To allow this ruleset to still be used by projects supporting older WP versions as well as newer WP versions, they will - for now - not be removed from the ruleset. However, documenting what WP version introduced certain polyfills and where applicable in what version of WP they were removed, seems prudent.
Note: the JSON related polyfills will most likely also be removed in WP 5.3, but those changes haven't been committed yet.