Orbi - number of satellites and NETGEAR - Nighthawk Mesh X6S Tri-Band WiFi Mesh Extender

I already have have 3 satellites with my Orbi SRS60 router.  They work fine.  Would like to have 1 more, but know that Netgear says that a limit of 3 satellites on the Orbi system.  I have seen a new Netgeat mesh extender, the NETGEAR - Nighthawk Mesh X6S Tri-Band WiFi Mesh Extender.  Will use of this extender be OK and not technically be the addition of another "satellite"?  Thanks.