With a number format, a user could supply "-a'0'b 00.00" (as of a few releases ago). The first zero has to be quoted. But it would be equivalent to have "$'-a0b' 00.00", because the - wasn't a syntax character, until we made the semantic change in CLDR to allow replacement by the plus sign.
But by the action of formally changing in CLDR the minus to be a placeholder that we could swap out with a + sign, we've changed that. See
So we need to document clearly in CLDR (and have ICU point to that documentation) that for number patterns:
is not the same as