No, you're having a "Condition Inspection" done. There's no such thing as a "conditional inspection" - the inspection is not "conditional" on anything - it's checking the "condition" of the aircraft.
And that's the rule in the US - whatever the OL's say. If they say "per 14 CFR Part 43 Appendix D" (as almost all OL's do), then 43 (A) rules - not the AMM.
When I do CI's on Experimental aircraft, I note that the MFG's of seatbelts generally recommend replacement or refurbishment at 10 years. Most seat belts, on planes that are stored in hangars, will be in pretty good shape after 10 years. So _I_ do not require seatbelt replacement at 10 years - I recommend replacement on-condition. If there's any deterioration of the stitching or if the belt material is getting stiff, I'll recommend replacement, and require it before the next CI. But unless the belt is obviously torn or damaged, I won't refuse to sign the CI.
The A&P in an Experimental Aircraft CI has extreme latitude in deciding what's "In a Condition for Safe Operation" or not. They should use the AMM (if there is one) and 43 (A) as reference for making decisions on what's safe, but unless the OL's specifically require it, you don't have to do it merely because it's in some MM.
I don't think you're going to find anything in writing about these specific issues - the A&P is left with the judgement call on just about everything on an Experimental Aircraft.