1) How are they unclear? If you saw those would you not recognize the one as a US phone number and the other as a date?
2) It's not sound because this is not math. There are always an infinite number of .0's at the end as noted by 10.9.2 having a .2 after 10.9. If this was math it would be impossible as there is a single period (or comma, depending on your country/culture) used to separate whole from fractional integers. Again, if this was math you couldn't have multiple periods — unless you reverse the period and comma usage which would then mean they are thousands separators — or use letters as oft seen in version numbers.
1 There are various instances where numbers are used with dots 126.96.36.199, so no, the American phone number format isn't always obvious to me. No doubt it is to Americans. The date format, even less so.
2 What? No! In maths, 10.1 is the same as 10.10 or 10.100000000 etc. In software, 10.1 is different to 10.10. How is that not confusing?