This post admittedly addresses an incredibly niche scenario, I was pleasantly surprised by this discovery and decided it was worth a sharing in the shape of a small blog post. This is loosely related to the Apple TV request to blast IR commands.
I find it hard to comprehend why the Apple TV 4 and 5 (4K) will only allow a single Siri remote to be associated with the base unit? Especially when you consider the gaming platform potential of the Apple TV. I recently attempted to pair two Siri Remotes to my Apple TV and... yep, I can confirm that at the time of writing December 2017, the Apple TV does not permit multiple Siri Remotes to be connected.
However, in this (my) extremely niche scenario, there is a soundbar and this unit will only receive volume change commands via IR. When you pair a Siri Remote to the Apple TV, the IR command set are transferred to the Siri Remote via Bluetooth. After my dual Siri Remote experiment, I was pleasantly surprised to discover that the IR command set did not get removed during the un-pairing of the second Siri Remote.
This has positioned me with 1x fully working Siri Remote and 1x (soundbar-volume-only) IR Siri Remote control. And this is OK! It has saved me from acquiring an additional Universal (programmable IR) remote control.