I'd guess that's down to both Renaissance artists and early graphic designers faced the same difficulties in trying to make symbolic reference to things without access to colors/paints/dyes that would otherwise be used. (As in the case, say, of a family with a colorful crest that wanted a copper crest to replace their cloth one. The colors have important meanings but the copper could not be colored so they needed a way to preserve the symbolism of the colors in the copper version)

We see a similar thing in games like DwarfFortress where the designer doesn't have access to dwarf/goblin/dragon/water/grass/etc sprites and so has to decide upon a stand-in.

I can't find anything pointing directly to her using heraldic patterning, but it seems her primary reference was Henry Dreyfuss’s Symbol Sourcebook (1972) [limitted preview on archive.org, full available for sale and elsewhere].

And while the book does not specifically feature heraldry or the hatching specifically, several of the examples in the text do contain very similar dot and line patterns as fill in various shapes. Pages 50/1 feature several iconic patterns to indicate earth, rock, natural rubble, rubble, cast stone, marble, slate, brick, common brick, face brick, fire brick, glass, grass, various woods etc in arhcitectural drawings.

There's a surprising durability and universality to certain symbolism. A stick person engraved in the pyramid is reckognized today. Hatching and cross hatching have been used to indicate shadows for hundreds or perhaps thousands of years.