Controversial digital art take, whining
The medium is digital art, not Photoshop. Focusing on specific brands of program only benefits big tech companies and discourages competition. You don't see trad artist books saying they'll teach you how to paint with 'winsor and newton inks' and hyper focusing on flow rates and how much it absorbs into W&N brand paper, do you? Well you do but not nearly as much as books purportedly about digital art technique and skills are just PS technical manuals...
Trans woman, bisexual, someone's fiancée, forever a programmer, poly, and former total mess