That would entail adding a branch instruction and risking a cache miss on every single video playback in order to save a couple hundred bytes in a data stream at least four orders of magnitude larger.
Speculating? I think branch predictors would eat this for lunch
Hence, my use of the word "risk".
Why not also show the same video title, thumbnail, content, comments and side bar regardless of the video URL?
I mean, it's an Easter egg. These things aren't known for their practicability. If one were to object to this, it's because it pushes unnecessary computational costs on every single end-user device that has to render that CSS since the comparison and branch now happens client-side at page styling time. I wonder how many billions of CPU cycles that's wasted.