Verifiers come out of an accredited pool by rotation, and the registry pays them. A developer never picks one, never pays one, and doesn't know who is coming.
Across most of the voluntary market the developer picks their verifier and pays the invoice. Everyone can be acting in good faith and the pull is still one-directional: a verifier who writes hard findings is a verifier who doesn't get the next job.
Financial audit settled this decades ago by separating who picks the auditor from who gets audited. We copied it. Verifiers are drawn by rotation, the fee comes from a pooled levy on issuance, and no developer can request or refuse a particular firm.
It costs us more and it slows issuance. It is also the only kind of independence that holds up when somebody asks how it works.
Next layer
Verification finishes with an attestation. The registry is where that becomes permanent, and where anyone can go and check it.