I have used Lab space in Photoshop a bit. You are right... it is a relative to Munsell. Lab has one or two very particular uses in color adjustment. For example

I have used Lab space in Photoshop a bit. You are right... it is a relative to Munsell. Lab has one or two very particular uses in color adjustment. For example... as lightness is completely separate to chromacity, it is a very agreeable space for lightness and saturation adjustments. It is also great for demonstrating to students how the perceptual Lightness value of a hue differs to the lightness value indicated by a desaturation in simple RGB space.