In short, why does 0.12 format as "0.12" instead of ".12" when textNumberPattern is "#.##".  It would seem that "#.##" would mean the leading 0 is optional. But it doesn't. 

ICU chooses the minimum number of integer digits to be 1 even when the textNumberPattern has "#" before the decimal point. 

ICU team did not resolve this either way, the bug I reported there remains open: https://unicode-org.atlassian.net/browse/CLDR-17309 

But, this would be a significant change in ICU behavior, so probably cannot change in ICU without requiring a switch be thrown to enable it.