Can untidy cable bundles interfere with cooling?

Yes.

A few neatly routed patch leads are unlikely to trouble anything. A large, dense bundle draped across ventilation openings can obstruct airflow and make access to the equipment harder.

The rear of a cabinet is particularly easy to neglect because it spends most of its life out of sight. Give it enough spare cable and enough time and it can develop what appears to be a self-supporting ecosystem.

Keep the vents clear, support the cables and remove unnecessary excess where practical.