Kefir is similar to yogurt but different from it.
You must conform to the law and not deviate from it.
I'd guess it's the influence of Spanish, which uses "a" (~ "to" in English) for almost everything.
But you're right — I've heard some native Spanish speakers say "different to", and it's likely because they say "diferente a" not "diferente de" (where "de" typically translates as "from").
This situation raises an interesting philosophical question: is it ungrammatical for a native Spanish speaker living in CA to say this? I have always considered it to be an ungrammatical/incorrect usage. But coming from a British person I wouldn't consider it incorrect. I would consider them to be speaking a different dialect of English.
If a student said this in an English literature class in CA, my guess is that the teacher would correct the native Spanish speaker but not correct the British student. Or at least this would be my intuition as a native English speaker who studied linguistics a decade or two ago!
A personal data-point: I'm a native English speaker from norcal/oregon, and my wife is a native Spanish speaker from Monterrey, Mexico.
Since learning Spanish and being exposed to her good, but definitely not native, English, I didn't even notice "different to", and it doesn't seem particularly "weird" to me. But if I think about it I'm pretty sure it would've seened very weird to me back when I was in Oregon!
(It goes the other direction too. E.g., she's caught herself saying "vino rojo" instead of "vino tinto" and "hacer linea" instead of "hacer fila".)
In general I think it's pretty common when two languages are in close-contact to get some cross-contamination like that.
And prepositions are often pretty arbitrary.