timedelta marks time in days, seconds, and microseconds. It doesn't take leap years into account because the concept of years is irrelevant to timedelta. If you need to account for leap years, you need a different API.

The comparison is somewhat awkward, because the rails example presumably produces a date, while the python one is referring to an interval of time.
Just from the meme it's not obvious which was the actual intended use, so labeling either as inaccurate requires us to make assumptions.

Personally, the concept of "10 years ago" is a bit nebulous to me. If today is February 29th, is ten years ago March 1st? Doesn't seem right. Or particularly useful.

Because what's accurate here depends on the context, and the Python example doesn't hide that from the programmer.

The same dilemma goes for month calculations: does "3 months ago" mean 90 days ago, 91.3 days ago, this many days into the target month, or this many days from the target month's end (e.g. to account for 28, 29, 30, and 31-day months)?

Does the Ruby version do that though?

I haven't got it installed to check, but seeing constants like SECONDS_PER_YEAR in the documentation makes me think it's just as bad if not worse.

https://api.rubyonrails.org/classes/ActiveSupport/Duration.html