Board Game Arena

Some actions that needed to be done by all players can be organized in parallel (e.g. like in the 7Wonders game)
For example in Cities and Knights:
- When > 1 players have same points in winning barbarians, they need to choose a card. Now it happens sequentially
- When players play some cards like Wedding or Commoditiies trade

After a win against the Barbarians the players take their bonus card in turn order. This is clearly stated in the game rules - thus it is implemented correctly on BGA.
If you are the last player in turn order you might base your decision at the other players choices. Say, all players before you have taken blue progress cards (Politics) then this might influence your own choice.

Implementing this choosing process in parallel would change the game rules.

"Wedding" (blue progress card) is already implemented in parallel. The clock simultaneously starts for all players that have to give you 2 cards. All these players may choose independently and at the same time.

With Commodities trade you probably talk about "Commercial Harbor" (yellow progress card) that allows you to offer ressources for commodities. Again this is implemented correctly on BGA according to the game rules. You can offer a ressource to each player and he has to give you a commodity of his choice. First you choose one opponent and offer him a ressource. Depending on the result of this offer, you choose the next player to trade and so on. At any time you can stop trading - you do not have to offer each player a card.

If you only want 1 certain commodity, you will stop offering your valuable ressources for potential commodities that you might not need.
And if the first player has no commodities at all, you can offer the ressource of the first trade in the 2nd trade. Say you have one of wood, clay and sheep. If you offer the first player a wood and he has no commodities you keep your wood. Then you can offer the same wood to the 2nd player.

Both my examples show that the "Commercial Harbor" card cannot be implemented in parallel without changing the game rules.