Embedded players have become a standard fixture of the article page. What they should look like once they get there is still an open question.
Three networks, three explanations, and a measurement standard that nobody involved seems willing to defend in public.
A rail module is handed a fixed width and a fixed height by a template nobody has revisited in years. Everything else follows from that.
On a wide desktop the rail is 352 across. On a tablet it is closer to 221. Below that it stops being a rail at all.
Announce itself, or stay quiet until asked. The designs disagree, and the disagreement is the interesting part.
The same module gets 300 pixels on an article page and 150 here. Nobody can say when that was decided, or by whom.
Template decisions outlive the teams that made them, and the rail is where you can see it happening.
The cheapest way to avoid shipping a player that only works in the file it was drawn in.
Some of it is dark, some is nearly white, and a good deal of it has text baked in already.