Hi Zenfishbike!
So the main concern I'd have with veneering the sides of Oticas without finishing the inside, is moisture absorption and desorption.
For instance. You take a 4'x8' sheet of raw MDF. You apply veneer to one side. That side will absorb less moisture than the raw side. So if you have more moisture in the air than the sub-straight (MDF), it will absorb more in the raw side, causing it to swell, and turning it into a banana. It will go the opposite direction if you're in a dry environment where the moisture will desorb, causing it to pull, creating a banana in the opposite direction. That's why you will always see some sort of backer that matches the absorption properties of the veneer/laminate/vinyl on the unseen side of, say a countertop.
UNLESS you have enough bracing to counteract the pull of the sub-straight, or it's a small enough area that this won't really matter.
But, for the Oticas... The bottom of the side panels would be fine. They're adequately braced to prevent any pull. The top sides? Can't say for sure honestly. I don't see the side that's scalloped out pulling at all; it's only a few inches wide. But I'd (personally) have a slight worry for the "full" side top corner pulling one side or the other over time. But, this may not really matter, and the pull may be so minimal you don't even notice it.
I'd personally run them 100% raw until you are able to fully finish them in an adequate timeframe.
But then again, everyone that I've seen that has veneered them doesn't balance the panel with a backer. It's all painted on the insides. So, are any truly balanced? No. But the paint CERTAINLY helps. Just not an industry standard with cabinetry.
So does it matter? Probably not... but it would probably keep me up a bit at night