Tolerance for weldment's angular dimension

[EcoMan]

Hello,
Why does ISO 13920 say that the length of the shorter leg determines the applicable tolerance for the angular dimension of a weldment? Wouldn't the deviation be dependent on the longer leg?

 

[CheckerHater]

Because the longer leg is acting as implied datum.

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[EcoMan]

Thanks, CheckerHater. My shorter leg is on a datum, so I'll base the tolerance on my longer leg.