[q3k]

I don't know (definitely not a native English speaker), but Wikitionary seems to agree with me: https://en.wiktionary.org/wiki/second_to_last#English .

[gwright]

Well, I think you may be right. See my edit above. I suspect this is a regional usage pattern and I've just always been in places where "next to last" would be used and not "second to last" so I was thinking they were different, but they apparently are the same!

Learn something new every day.

[gwright]

Here is an ngram analysis with a British corpus

https://books.google.com/ngrams/graph?content=second+last%2C...

And here is one with an American corpus:

https://books.google.com/ngrams/graph?content=second+last%2C...

[q3k]

Nice tool. You should expand the search range to include 2018/2019. Quite a significant change happened since then.