In general it means that the seller shall select the third party services involved with the transaction including but not limited to, the escrow company, title insurance provider, pest control inspector, natural hazard and zone disclosure provider, and even the provider for the home warranty.
It doesn’t mean you cannot ask to select the providers of these services. They are kind of just giving you a warning shot across the bow that they want to select the services.
Everything is negotiable.
Of course service providers for YOUR side of the transaction like financing and your inspections are your choice.