Hm, good point. I generally go on feeling, from an English as an Nth Language point of view... and my subjective feeling is that "snuck" has more of a "participle" meaning, while "sneaked" has more of a "past tense" meaning.

According to AI Overview, there might also be some EN-US vs EN-GB at play:

"Snuck" is an irregular past tense: It's an alternative form that has gained widespread acceptance, especially in North American English.

"Snuck" is sometimes considered nonstandard in British English: While it's increasingly common in British English, it's still often seen as nonstandard in formal writing.

That would match the Wiktionary entry: https://en.m.wiktionary.org/wiki/sneaked