Solar panels can only be wired in series/parallel if they're identical panels receiving the same amount of sunlight. Otherwise, the whole will be limited by the panel receiving the least sunlight.
So if you have two solar installations in different places, perhaps with different angles and orientations, then you do need two inverters.
Besides, you can't parallel 12 panels and 14 panels, and you can't wire them in series either because with the usual voltage being 40V, that would make too high voltage for one inverter.
Fronius primo is nice, in fact I just bought one, not installed yet. I think it's a good choice, reliable brand. It has a documented interface over the ethernet port, so you can query it and know how it's working and what power it is generating without any cloud garbage. This can be useful if you want to switch loads in your house when there is PV power so you consume what you produce.
Injecting current from both installations in different phases makes sense.
However I don't know what you mean with battery, since Fronius Primo doesn't do batteries. In fact it is an injection-only inverter. If there is a blackout and you lose mains power, it will shut down. This is mandated by law: if the inverter kept injecting power into the mains when it goes down, then workers from the electricity company would get electrocuted when they cut power to work on the lines, and you would be responsible.
So your installer is doing a good job if what you ordered is a system meant to lower your electricity bill. However this will not provide power in a blackout.
The circuit breaker in the picture says you probably live in Europe, so if you've been following the news and you anticipate blackouts, then you need an inverter that will still work without mains. If this is the case, edit the question and @ me, I'll add to the answer, because I had to do all of that last month.