Howdy,
This seems like a direct cost/benefit analysis where silent compliance fails the test.
...so don't be silent!
Have the conversation (including everything in your post) with your OEM customer...BUT !!!
The following people should be at the meeting...don't leave a single one out...delay the meeting until all can be there:
1. Your customer SQE
2. Someone in Engineering management using your product (NOT engineering...engineering mgmt).
3. The purchasing agent
4. Someone else in Mgmt at the customer who you get along well with.
Talk to #4 first and get him/her on board with the goal of the call: "Waive this requirement".
OEM's can (and do) bend these rules everyday.
Don't present the cost case...let #4 above present the cost case. OEM's wont listen to you, but they will listen to their own managers...purchasing dude and SQE are deathly afraid of managers in most cases...so let him/her make your case for you.
Have a private chat (after you've done your calcs) with your management friend and walk them through the additional cost to you, and how you have no choice but to pass that cost on if they insist on this path.
As soon as that topic is broached (by #4, not you), the purchasing agent will cave...their performance review is based on cost savings, the potential increase will scare them into line.
#2 above doesn't care about price, they care that your parts work on time...and can vouch for that.
Prep the topic with #4, open the topic of IATF on the call, then let them convince themselves.
BTDT with Tier 1 and OEM...this approach works.
#1 knows what loopholes (waiver) they can use
#2 knows that your products are good already
#3 is scared of a price increase if they insist
#4 has the clout to ask the hard question
HTH