Saying “10 times” implies multiplication -i.e., that X becomes larger. So when you add “shorter” to that, it directly contradicts the expectation set by “10 times,” which implies an increase.
You may see it that way as there is some kind of "turn" in this expression that you have to follow mentally. It is because it contains a form of negation. But to call it misleading is more of a personal interpretation than a fact.
It is no more contradictory than "
I do ...
not", where the "
I do" is contradicted by the "
not". Most negations have such a pattern.
Obviously "
ten times shorter" is fully equivalent to "
10db less" or “
reduced by a factor of 10” the latter you gave as a clear and unambiguous expression.
Talking of mathematically correct, shouldn't it say "reduced by a
divisor of 10" or "reduced by a factor of
0.1"? (Just to put on my pedant hat.)
To call some of these expressions "clear" and others "unclear" is a matter of personal taste and, as was pointed out before, depends on the context.
You might choose to avoid the negation here by using a fraction (one-tenth) but then the expression does not get simpler (or better) as a fraction contains two parts that have to be brought into the correct relation mentally too.
So you may do as you seem fit, but
accept respect the choice of others too.
