why standards such as DoD and Gutmann are not necessary?
DoD standards exist because data containing government secrets must be protected against hypothetical future threats of being breached (even if said hypothesis are defunkt).
Gutmann's standard exists because Peter Gutmann didn't understand HDD technology and based his theory on a massively oversimplified concept of how he assumed a hard drive worked. It turns out, he didn't know how a HDD worked, and his paper was immediately met with a fierce rebuttal by actual experts. Regardless, the damage was done, people had read his paper and software devs had already started writing software to waste gigawatts of electricity wiping HDDs for days on end unnecessarily.
Those who've attempted to use MFM to read such hypothetical "trace patterns" found that a simple coin toss had better odds of guessing the correct data compared to their MFM readings. Zero-fill is more than enough.