Because the 48" 65w bulbs are power compact bulbs. T5ho bulbs in 48" are 54w.
Another way to tell is by looking at how the bulbs go into the fixture, power compact plugs in on one side, t5ho/t8/t12 all have contacts on each side of the fixture that they have to go into.
Also I don't know anything about SW
lighting so I can't really say about how good that is, sorry.