Seal weld refers to a weld's function just as fillet is a type of weld. The weld MUST meet the AWS requirements; the code does not allow violations. Reference AWS D1.1/D1.1M:2010, para. 5.14, "...weld size shall apply in all cases, unless the design drawings specify welds of a larger size." Whether by design or not, all welds will be sharing the load.