Hi Mike,
the VariantCond of the resource variant contains the answer: It is set to WebGL, true. This means, the condition is always true! See description of VariantCond operand value true: The condition is always true regardless of any other operand specified in the attribute. The variant is considered as being permanently active. In other words, the original member is overridden statically.
Set the VariantCond only to WebGL and you should get the expected result.
Best regards,
Manfred.