When 2 solar panels are connected in series.
If the data sheet for a single solar panel said it produces 12 volts (for example under certain lighting conditions) into an open circuit you probably wouldn't be surprised.
If the data sheet also told you that the maximum output current (short circuit) is 1 amp you probably wouldn't be surprised either.
The data sheet might also tell you that the maximum output power is at 6 volts and 0.5 amps. Would that be a surprise?
So, if you put two of these solar panels in series you would expect 12 volts at a current of 0.5 amps to achieve the maximum output power. In other words, the current doesn't change if you want maximum output power.
If you tried to get 1 amp from the dual panel you would have to short out the whole panel and that means zero power.