Split phase or Single phase ?

My new SMA Inverter is back feeding 120vac back into the grid with two hot wires (120vac ea ). Calling it 2 single phase (or poles) could possibly mean that it could be connected to either one of the 2 hot buses. Since I believe the Idea was to distribute the heat equally between the two buses then breaker slots next to each other, was a no brainer way to do it. So if power was going in instead of coming out it would be a 120/240VAC split Phase, but this never happens.
Comments
Remember that almost all US modern homes are wired 120/240 VAC split phase. L1 to neutral is 120 VAC, L2 to neutral is 120 VAC. L1 to L2 is 240 VAC... L1 vs L2 are 180 degrees out of phase, so they "add up" to 240 VAC when used as power source.
https://en.wikipedia.org/wiki/Split-phase_electric_power
If you did not use L1 from first bus bar, and L2 from the second bus bar... (i.e., L1 from bar1 and L2 from bar2), you would get zero volts between the two connections.
For standard two pole North American Breakers, L1 is Bar1 and L2 is Bar2 connections. So you always see 240 VAC between L1 and L2.
https://www.homedepot.com/p/Square-D-Homeline-2-20-Amp-Single-Pole-Tandem-Circuit-Breaker-HOMT2020CP/202353308
-Bill
Just like taking two D Cell batteries end to end in series. Call the center connection between the two batteries Neutral.. V1 to N = +1.5 volts; N to V2 = -1.5 volts; V1 to V2 = 3.0 volts.
-Bill
Thank you very much now I get it.
-Bill