By definition, MIDI OUT will output MIDI data generated by the device in question.
The MIDI OUT jack on the refaceCS is no different. It sends OUT data generated by the reface CS.

By definition, data arriving at a device’s MIDI IN will typically be used by the device itself.

In order to trigger your “midi tone bank” with your sequencer you need to connect the MIDI OUT of the sequencer to the MIDI IN of that device.

If the refaceCS had a MIDI THRU Jack (by definition this is an additional MIDI port that allows incoming signal to be passed through the device and travel on to the next device in the chain. Unfortunately, for what you want to accomplish, the refaceCS does not have a THRU port.

Alternative solutions are:
Connect the sequencer directly to both devices. You say you want to use the refaceCS”s PB control, most pro sequencers allow you to re-route incoming MIDI signal from one device and allow you to trigger any other connected devices.

For example, Cubase running on a computer, or tablet, would address both devices directly, all routing of signals would take place in the sequencer software. Meaning you would send PB messages into the sequencer, and the sequencer would route that signal back to the refaceCS, or on to the other tone generator device or you could route the signal to both devices.

You don’t mention what your particular sequencer is...nor do you mention how you are connected. The refaceCS has both standard 5-pin MIDI IN/OUT and USB-MIDI IN/OUT (for use with a “Host” device, computer/tablet)