There are two sources of error here:
1. Your interpretation is essentially "computers struggle to complete tasks that are impossible for them to complete" - a meaningless tautology. At best it is "nothing scales infinitely" which perhaps is a bit more useful as a refutation for complaints that something "doesn't scale" in an unlimited fashion, but that doesn't seem to be the context here.
2. "Too large" is ambiguous. If it's "too large for computers to handle" then it devolves into the above meaningless tautology. However, a sensible and common interpretation would be to interpret "if <something> is too large" as "if <something> is very large" - but we know that computers can in fact handle numbers with huge digit counts (somewhere between 1 and 60+ million.)
So the original statement is either a largely meaningless tautology or something that is misleading and/or incorrect. PP's criticism is valid.
I don't know whether you mean "teach" or "tech" here, but this seems to be an ad hominem argument.
Regardless, I would submit that clarity and correctness matter both in teaching and in tech.
Correctness, of the sort you are implying are absolutely not appropriate at all levels. There’s a reason kids in second grade are told that you can’t subtract a larger number from a smaller one, for instance.
2. In grades 1-2 (iirc) we applied negative numbers when we talked about the number line (which we had on the wall.) Even preschoolers knew about negative temperatures on the thermometer.
3. See PP's original comment.
You don't need to tell kids things that are misleading nonsense. It only confuses them more. You can be precise and high level at the same time.
In no sense do computers struggle with digits. That's a misleading confusing statement and it's not appropriate at any age.