A tag should describe the question, not the answer.
Some translations by Google are actually correct, especially if you take a direct quote from the Vulgate or something similar.
Therefore I think the relevant tag would be google-translate-check, asking "is this translation given to me by Google Translate correct?".
We already have the tag translation-check with a good number of questions.
The new one would be a "subtag" in the sense that it specifies it further.
It is not a problem to have tags at different levels of generality.
I am not fully convinced that such a tag would be useful, for three main reasons:
You can already search for questions containing the word "Google" and the tag translation-check by typing
[translation-check] google is:q into your search bar.
You can indicate tags with square brackets and words as plain words, and the flag
is:q restricts it to questions.
If you need any help using the search tool, don't hesitate to ask a meta question or drop a message in our chat room.
You can also read the manual.
There is also a list of questions linked to the one about Google Translate.
Actually one of my goals when asking that question was to create a universal reference to which we can link whenever Google Translate nonsense shows up.
A similar list exists automatically for all questions.
Are such questions really all that different from other translation checks?
I'm not aware of Google using information like this from non-Google sites to improve their translations.
If with suitable tagging and formatting of our questions and answers we can make the popular online translation tool more useful with Latin, then I support it.
Machine-reading might not be all that useful, as answers are often more nuanced than "here's the right translation".
And context often matters a lot, and neither a machine nor a human can consistently translate mottoes right or even sensibly without context.
If someone knows how Google Translate learns, I'd be happy to read more.
If SE tags play a role in Google searches, maybe adding the tag would help.
If there are users who would find such a tag useful for their own personal use (thus making no assumptions about Google), then it sounds like a good idea.
Or if you think it would make it easier to answer questions if translations by Google are tagged as such, that is a sound reason as well.
Finally, I should mention that there is little to no harm in adding a new tag.
There shouldn't be any major cons.
What would be the pros to you, the users?
I am not against creating the tag, but I wanted to make sure it's created for the right reasons: describing questions and helping users, not describing answers and helping Google.