Yes, you can connect to an XLX reflector with D-Star without having to use an XRF or DCS connect string! This is a supported feature of ircDDBGateway (which is leveraged by the Pi-Star distribution).
If you’re running a recent version of ircDDBGateway (such as the one in Pi-Star 4.1 releases), you can connect via an XLXnnnmL type command.
In this case nnn is the 3 digit reflector number and m is the module letter.
ircddbgateway will then use DCS to make the connection to connect to module A of reflector XLX020.
For this to work properly, be certain that the following is set in your ircddbgateway config file:
You can check this in the Pi-Star expert mode configuration for ircDDBGateway.