I think the problem isn’t so much saying “I see your bet”. I think the problem is the compound sentence with numbers and also throwing in chips at the same time, oftentimes making an illegal raise.
“I’ll see your 20,” throwing in 20, “and raise it 30 more,” throwing in 30.
https://youtu.be/35wRdXm1UpE
Also notice saying “see it” to call a bet.
I’m guessing that this expression used to be more popular and now has fallen out of use in casinos because it makes you appear to be inexperienced. Also procedure teaches dealers to use the word “call” to verify action. It’s sort of how in America, we say fold, and in the UK they say pass. I’m sure that if you say “pass” in an American casino, that would still be verbally binding.