What I'm surprised about is this seems like it would be significant, highly proprietary intellectual property for Home Depot.

Facebook is highly likely tagging those users as "home improvement interested users" and targeting entities buying ad placement for home improvement goods/remodeling services (i.e. Lowes and independent remodeling contractors) who would compete directly against Home Depot itself.

Or at minimum its recursive because Home Depot's marketing side will probably at some point pay Facebook extra for this data.