...

Microsoft's time zone information cannot encode penultimate Sundays,

a "POSIX-style" TZ environment variable string can't encode it either! Does zic omit the recurring rule string from the end of the version 2 tzfile in this case?

zic does indeed omit the rule string in such cases. Examining such omissions is a way of identifying areas where the POSIX specification might be usefully extended (for example, recognition of a 'u' element in a time of day to specify that it's universal time--this would allow a POSIX-style Godthab rule). --ado