Let's spell out blanching.
Water soluble vitamins are reduced. C, B
Fat soluble vitamins are Protected A D E K
Some reduction in Anti-oxidants
Plant sterols are protected.
Minerals can be reduced but if you blanch in hard water, unlikely.
Nutrient loss starts as soon as the veggie/fruit is removed from the plant and cutting them makes it worse. So blanching soon can actually help you out in some ways and increase minerals like calcium if blanched in hard water.
Blanching still looks better than throwing it away and the losses may not matter. Many use a supplement. Without knowing the weight of everything eaten, starting total nutrient available, blah blah blah we are only guessing and making reasonable attempts to satisfy need. What's to say that a dragon isn't getting more than he really needs with fresh and supplements(wasted money) and blanching to reduce waste and supplementation isn't sufficient at lower cost.