It's not a myth. I run GrapheneOS, and my bank app doesn't work, the Blind app doesn't work, and another common marketplace app (not amazon) has shadow banned me for using it on a device without hardware attestation. I only found out after reaching out to support and having a lengthy conversation with them.
It's idiotic that they require hardware attestation, but let's not fall into the trap of "it worked for me".
Even with these limitations, I'm okay with continuing to run GrapheneOS.