Are Paradox revoking keys for their games, specifically Cities: Skylines and Europa Universalis IV?

They aren't real removals or revocations. It's a failure in the sync.

I've had hundreds of these "revocations" this year for DLC and OST. All false. Nothing was actually revoked from Steam. Just wouldn't sync so barter.vg thinks they are removed. Steam stops reporting the DLC and OST during sync. Don't know why.

Happens on isthereanydeal.com too.

I've only had a couple of true revocations where there was a "price error" and the store refunded the purchase and had the key revoked. Most of the other "removed/revoked" are games that steam bans or get delisted.

The revoked or removed counter is not a reliable source.