xdotool search cannot find Steam Big Picture Mode

[dollhaus]

When I run xdotool search "steam", xdotool spits out a number of PIDs. Assuming Steam Big Picture Mode is running, finding the appropriate PID through trial-and-error and running xdotool getwindowname <pid> returns Steam Big Picture Mode.

However, xdotool search "Steam Big Picture Mode" returns nothing. The same is true of using any of the words in that search term alone, excepting "Steam".

Arch version Linux 6.11.2-arch1-1 x86_64
xdotool version 3.20211022.1

[FascinatedBox]

What is the output of xprop on a Big Picture Mode window?