Can we talk about how nobody scrapes their cast iron after cooking

I was cleaning a client's kitchen in Fair Oaks on Tuesday and her cast iron skillet was sitting on the stove with a quarter inch of old bacon grease caked in it. She said she never scrapes it because her grandma said the layers add flavor, but those layers were gray and sticky and smelled like a wet dog. I cook on cast iron almost every night and I scrape mine down with a metal spatula while it is still hot, every single time, and my pan looks like black glass after 4 years. The crust she had built up took me 20 minutes with hot water and a chainmail scrubber to get back to actual iron. I am not saying you need to baby it, I am saying the seasoning you want comes from thin layers of oil baked on, not from leaving food bits to rot. So where did this idea come from that scraping a pan ruins it, and has anyone here actually tested it side by side?