The “theatrical backdrops for complex ceremonies relating to status and prestige“ is a bit oversimplified I think, at least for continental Europe. In German, for example, we have two words that translate to “castle”: “das Schloss” is a representational building, but “die Burg” describes a military fortress, which often were small, plain, very well fortified buildings with multiple clever layers of defense. There’s no confusion between the two even though many Schlösser had Burg-like features for decoration. It’s perhaps also not a surprise that the article’s examples for representational castles are mostly from England, I think Britain’s military history is a bit different from that of the rest of Europe.
English has the same basic distinction: "Burg" = "castle", "Schloss" = "palace".
But upon having a closer look, things become complicated quickely: "Schloss" ist typically used for unfortified residencies starting in Late Middle Ages/Renaissance. But there existed unfortified residencies since the Early Middle Ages inside towns. The term for the early imperial or royal palaces is "Pfalz", which has the same Latin root as "palace": "palatium". Sometimes the term was also used for the residency of a bishop.
Then there are castles that were both, strong fortresses but very representative. Nuremberg castle, Trifels and the Wartburg are examples of these, or from a later period Heidelberg. Sometimes a castle was later converted into a sort of palace by tearing down walls.
The terminology varies in such cases. The "Heidelberger Schloss" (a strong but also very representative fortress) is called "Heidelberg castle" in English, "Schloss Mespelbrunn" (a converted castle) is called "Mespelbrunn castle".
There is also a rarely used standing expression "Veste" ("fortress") used as a title for some specific castles (for example "Veste Coburg").
I agree with the parent that the “theatrical backdrops for complex ceremonies relating to status and prestige“ is a bit oversimplified. But we need to keep in mind that the function of a castle is typically very complex. And the "theatrical backdrops" is an important one. That their defensive value was quite limited could be seen during the German/Austrian passant revolt in 1525 when thousands of castles had been destroyed in a couple of months, while the aristocrates nevertheless won the war in the field. Typically the castles had only a handful of defenders and quickely surrendered, or the aristocrates just fled and did not even try to defend their castles. Only some strong, well-manned fortifications hold out, often just barely like fortress Marienberg in Würzburg.
