Think it isn't as easy as 'good fabric'.
For instance, my Sic Tess and T Mason oxfords are generally a dream to iron compared to the Alumo poplins.
OTOH, my white shirt in 2-fold 80s Alumo poplin is much easier to iron than the white shirt in 2-fold 120s Sic Tess oxford.
Then again, my two patterned Sic Tess oxfords (also 120s) are easier to iron than said 80s Alumo poplin.
Many a time, you have to trust your shirtmaker to give you an accurate lowdown on what you're buying. As Charles Nakhle often says, certain cloths 'love' the iron.