As with any live service game in its infancy, Overwatch 2's devs are learning as they go. It might be a sequel, but since the original wasn't free-to-play, there's very much a learning curve involved. A learning curve that may well involve reassessing the reintroduction of the first game's credits. Many players have been left confused, not knowing the difference between the old way of spending and Overwatch 2's coins.
Most live service games have more than one type of currency, so it's certainly not out of the ordinary that Overwatch 2 would do the same. The logos for the currency are also different enough that they shouldn't be confused. Round white circles for the returning credits, and golden hexagons for the premium coins.
It's what feels like an unnecessary deviation from that color scheme for the sake of the season three battle pass track that has caused confusion. As pointed out by PCGamesN, there are credits to be earned via battle pass progression in season three. However, for some reason, the symbol for them on the battle pass has been turned gold, leading players to think there were actually the far more coveted coins up for grabs.
Players have been sharing their disappointment during season three's first day upon learning credits have been added as a battle pass progression incentive as opposed to coins. While adding a second currency for players to earn is in keeping with other live service games, not giving players the chance to earn back the cost of a battle pass is not. Players need coins to buy the battle pass, and credits can only be used to buy select other items.
That means there is currently no way to grind Overwatch 2's battle pass enough to cover the cost of the following season's pass. Hopefully that will change in the future, or at the very least, Blizzard will alter the credits logo on the battle pass to prevent further confusion. On the bright side, whether you have a battle pass or not, you can play Loverwatch, a dating sim linked to the game created to celebrate Valentine's Day.