How do CFD Indices work exactly?

Does anyone knows how exactly CFD Indices work?

Broker A is telling me they will be having a dividend adjustment for their CFD Indices products.

For example, Taiwan Index CFD is currently trading at 400 points and there will be a dividend payout of 5 points in a few days.

Upon dividend payout, Taiwan Index CFD in Broker A will be adjusted to 395 points.

Whereas this doesn't apply to Broker B as Broker B says that they don't pay dividend for their CFD Indices products nor any dividend adjustment.

Wouldn't there be a tear in price when both brokers are selling the same product at a different price?

If it is a CFD over the cash market they should have dividend adjustment.
If it is a CFD over a futures contract (over the cash market) then dividend adjustment is priced into the price.

If it's a CFD over the cash market and they don't have a dividend adjustment that is something you may be able to arbitrage..