I wouldn't overthink it. However you cut it, they are good gains. I suspect the dyno you used is more truthful, perhaps a shade conservative. The tuner can easily put a bigger smile on your face with some creative coast down calculations, but that's just dishonest.
How long had the mods been on the car before it was dynoed (standard map)? The ECU can take ages to adapt to hardware changes. A good way to predict improvements is to data log the peak MAF value before and after the mods.
Maybe you could do a compression and leak down test to make sure the cylinder sealing is healthy. Might not be a bad idea to data log actual and requested boost pressures to see how quickly the target pressures are met. Worn out, lazy turbos can take a while to hit them compared to a new or low mileage one.
So before questioning the map, let's get some data logging and physical checks done
If it makes you feel any better, my ED30 made 230hp standard and with Revo stage 1 it only showed 290hp on the dyno. Am I dissapointed? Absolutely not. I care more about consistency than I do pub numbers. When I had stage 2+ it wasn't great, and the ECU just adapted it down anyway. The bigger numbers you can sometimes drive away with on the day, seldom stay that high. Some tuners are aware of this and just don't push things into that territory.