This card is broken. My dragon spirit of white has stopped being treated as a blue eyes after fiendish chain is used on it. I could no longer synchro with dragon spirit of white, because the cards text of (this card is always treated as a blue eys monster) was treated as an effect instead of a statement of fact. Thus that "effect" was nullified by fiendish chain.
Doesn't make that card "broken" (ie too op, "unfair" etc) in any way, you dumbass. Any card that negates effects would do the same thing as FC.
Also dragon spirit of white's statement IS an effect.
The same thing happens to cyber dragon core (this card's name becomes "cyber dragon") if you negate it's effect, machine duplication can't be used on it to bring out 2 real cyber dragons.
Yes, you have to distinguish between effects and Name conditions. And there are only very few cards that have a name condition:
https://yugioh.fandom.com/wiki/Name_condition
(PS: This is similar to Archetype condition which are non-effects too)