金剛經纂要刊定記 4.125

4.125

相是等者。謂三十二相蓋是鏡智之上所現影像，既墮有為之數，故當四相所遷，況對機宜有無不定，焉可將此而為法身，故言相是有為等，此釋經中如來所說身相也。

Regarding "marks are, etc.": this means the thirty-two marks are merely reflected images appearing upon the mirror-like wisdom; since they fall into the category of the saṃskṛta, they are subject to change by the four marks. Moreover, their presence or absence varies depending on the capacities of beings; how could this be taken as the dharmakāya? Therefore it says that marks are saṃskṛta, etc.; this explains 'the physical marks spoken of by the Tathāgata' in the sūtra.