Superlative adverb?

Greek Learning Greek
1

I came across this in Lucian, Dialogi Mortuorum 10.13:

ἀκούσῃ τῶν κυνῶν μετ᾽ ὀλίγον ὠρυομένων οἴκτιστον ἐπ᾽ ἐμοὶ

I understand what it means and I see that οἴκτιστον is an irregular superlative from οἰκτρός. But everywhere I look (e.g. CGCG 6.13), I read that superlative adverbs are identical in form to the accusative neuter plural of adjectives. What is the explanation for the form here?

2

It’s an internal accusative, so an adjective rather than an adverb, though it comes to much the same thing: making a most pitiable howling.

3

I like this term, “internal accusative.” I am bothered by calling it cognate when it’s not like “sing a song” or “dream a dream.”

Quick to the rescue mwh, thanks!