apply_filters ( 'jetpack_implode_frontend_css', bool $do_implode )

Notes

Instead of including a separate CSS file for each Jetpack feature, Jetpack enqueues only one file, built by concatenating all CSS from all Jetpack features. This limit the number of requests made when loading a site.

To deactivate this, you can use the following snippet:

add_filter( 'jetpack_implode_frontend_css', '__return_false', 99 );