I was informed today, a few weeks before it's due to be built. My only options were to cancel or accept and there was no offer of any reimbursement.

There was no mention of it being added at a later date but I also didn't ask.

I've just had the same thing happen for my Enyaq60 - they've removed traffic jam assist from the assisted drive basic package. Ordered in early July, confirmed build week 41.