That does seem to imply it. Unfortunately, I'm seeing contradictory info. in the LATCH manual (2007 edition) indicating the '06 Vitara and '06 Grand Vitara models have dedicated sets of lower LATCH anchors for the outboard rear seating positions only, and that Suzuki doesn't allow borrowing of the outboard anchors for a center lower LATCH anchor installation. Mind you the LATCH manual isn't always infallible, and a new edition of the LATCH manual is coming out in 2009 which may have updated info. about the Grand Vitara. In the meantime, you could try verifying with Suzuki directly that a center lower LATCH installation is allowable, and opt to use the seatbelt to install in the center. The other caveat is that the carseat manufacturer must also allow a center installation using the outboard lower LATCH anchors in cases where the vehicle manufacturer allows it.
FWIW, LATCH generally isn't considered any safer than a seatbelt installation, or vice versa, provided that you can achieve a proper install with less than 1" of movement at the carseat's belt path. It's also worth noting the LATCH manual indicates Suzuki does not state a lower LATCH anchor installation weight limit, in which case you would need to follow the LATCH installation weight limit specified by the carseat's instructions.