[jamesfinlayson]

I found it - in February 2023 it looks like added some limits and are enforcing that Steam customers don't get a worse deal than customers who use CD keys.

But yes they have clamped down on the fake games for trading card farming too.

[SXX]

It was a news in February 2023, but Steam had this as part of their ToS for decade or more. Basically Valve want you to run the same discounts on Steam as you run on other stores.

AFAIK it's perfectly fine to temporary run something like lowest-ever price outside of Steam on a condition that within some timeframe (not sure about timing) there will be similar sale on Steam.