They will definitely approve - i even do 1 claim and just 2x of the item in the description
I had a claim a couple of months ago with two items on the receipt that totaled $325.
Each item was under $300.
They only gave me $300 stating the reason was because there was a limit of $300.
I chalk it up to a stupid processor of the claim and definitely not work fighting.
I have had several other claims in the past that worked on the same receipt, but I tend now to order multiple on separate receipts, just in case an idiot on Amex's side doesn't understand the rules.
Also, I have seen it stated here before that you can submit the claim after 90 days as long as the dates you put in for trying to return etc, were prior to 90 days it would get approved.
I have two claims recently get denied for this. A different claim recently in the same situation did go through. So it looks to depend on who is processing the claim.