There's a vast difference between being able to control an anomaly 5 light years across and being able to control one that's 100,000 light years across. Being able to control and power something from outside the galaxy doesn't automatically mean that you're a Type III civilisation and more than our being able to run power grids between continents today means we're a Type I civilisation. In fact if anything the fact that the 10-C still need to conduct localised mining for necessary resources means they can't be a Type III civilisation.
Ah, but we're not talking about controling an anomaly 100 000 Ly's in size (btw, our galaxy is estimated to be now twice as big as that).
The DMA has a size of 5 Ly's. The 100 000 Ly's reference would be in creating Dyson Swarms around each and every star in the galaxy (and as such having the power of a Galaxy at your disposal)... which is an entirely different thing.
He was suggesting that a Type III civilization would have the necessary energy to create the DMA the size of 5Ly's, control it, and maintain an open wormhole to power it.
Its possible that making something larger than 5Ly's could demonstrate to be very hazzardous to the local environment though... so its possible that 10-C intentionally made the DMA the size of 5Ly's to encircle large enough amount of space, but small enough to not necessarily pose a threat to potential sentient life (but that would go contrary to what we saw in the Milky Way of its behavior... is it possible that they focused the DMA initially towards nebulae and similar phenomena and that star systems were their last resort (but that they simply didn't detect anything they would think of 'sentient'?).