SQF is really annoying with supplier approval. According to the code and guidance technically you get to define what criteria a supplier is approved under and you are only held accountable to following your own criteria, reviewing those criteria annually, and demonstrating through product quality history that you've verified those suppliers are still acceptable at some interval.
In practice, an actual supplier audit is industry standard and easy for CB's to audit against, and because it's so common they aren't used to having to think about your unique program, which often leads to "that sounds like BS so here's a minor".
It's really auditor dependent.
food grade valves, covers, and such that have direct and in-direct food contact
Here's what I'd do since pretty much all your "ingredients" fall under the same category. Do a detailed risk assessment of the chemical, microbiological, and physical hazards inherent to the materials, and describe how you control each of them through material composition, inspection, process etc. Then, type up a summary of how a "bad" supplier could actually affect these issues and limit "supplier approval" to collecting basic information like current contact info and a letter of guarantee ("I won't sell you anything dangerous or illegal and to the best of my knowledge it's okay to use in food processing equipment").
It's typically easy to maintain a register of contact info and have them simply sign a form letter, and if you've got a thorough risk assessment covering the risks, and the info you havedecided to collect is current on all suppliers, you should be able to get through the requirement.
One thing I see in your post that may have caused the auditor pause is that you approved them based on "delivery history". If you can show documentation that demonstrates you re-evaluate delivery history periodically as a metric that typically works, but usually this results in SQFP's saying something like "we haven't had issues with them", which is kind of a cop-out.
Dazzle them with paperwork and metrics on how many defective/late/unusable products each supplier has sent you in the past year, and it will demonstrate that you are actually auditing suppliers based on delivery history.