Inconsistency in TsDomain/TsPeriodSelector

[Immurb]

I discovered that TsDomain and TsPeriodSelector handle negative values for "Last" and "First" different from "Excluding". For "Excluding" the input '-X' means 'X years' which is consistent with the behaviour of other specifications e.g. "Forecasts horizon". For "Last" and "First" it is an invalid input and not the 'last/first X years'.
Is there any reason for that?

Besides the documentation for the method "excluding" is incorrect as it states that the input has to be "Greater or equal to 0."