One definitely has to wonder. We know that GPT-3 solves 1/2 digit arithmetic pretty much perfectly†; people criticized this very hotly as "it's just memorizing", but regardless, whether it learned or memorized arithmetic, that should apply even more to Gopher, which performs so much better and is larger. How can GPT-3 solve similar arithmetic near-perfectly and Gopher then be unable to...? Are we going to argue that "15 x 7" never appears in Internet scrapes and that's why Gopher couldn't memorize it?
I would want to ask it "15 x 7" outside of a dialogue or with examples, or look at the logprobs, or check whether "15 * 7" works (could there be something screwed up in the tokenization or data preprocessing where the 'x' breaks it? I've seen weirder artifacts from BPEs...). GPT-3 does not always 'cooperate' in prompting or dialogues or read your mind in guessing what it 'should' say, and there's no reason to expect Gopher to be any different. The space before the question mark also bothers me. Putting spaces before punctuation in Internet culture is used in a lot of unserious ways, wouldn't you agree 〜
I definitely would not hastily jump to the conclusion, based on one dialogue, "ah yes, despite its incredible performance across a wide variety of benchmarks surpassing GPT-3 by considerable margins and being expected to do better on arithmetic than GPT-3, well, I guess Gopher just can't multiply 1-digit numbers or even guess the magnitude or first digit of the result! What a pity!"
† quickly checking, GPT-3 can solve '15 x 7 =105'.