Dickgirl on male is when a dickgirl penetrates a male. That is the definition. Feminization is for when a male character becomes more feminine. That is the definiton. These two things have nothing at all to do with each other.

Dickgirl on male is sometimes seen with feminisation, but not always, one place it wouldn't apply is where the male is already very feminine and the Futa just dicks him down

I don't understand why you would suggest this.

dickgirl on male is a futanari (woman with a penis) having sex with a male, commonly, anal sex feminization is turning (normally, against their will) a male into a female not really related

I don't think that's how the tag works