See:
ports(7) FLAVORS
The FLAVOR variable is
not designed to contain configure options...it's designed to flag (possibly multiple) options in make to turn on and turn off groups of configure options. I'm surprised your method even works, to be honest.
What does "make show=FLAVORS" give you? I'm seeing a bunch of options to turn OFF features, but none to turn on features, suggesting that the default flavor is probably what you want (unless you decide to turn off a ton of features you don't need).