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Stock sequential primary turbo can hit high boost initially, but then boost will fade toward 2ndary turbo transition anyways.

You have ~220hp of airflow out of a stock primary turbo.

You can target high boost, but if your FD has other performance parts adding hp your boost will drop once you hit the right side of the compressor flow map well before the 4,500rpm transition.

You can bring transition rpm down lower so your primary turbo boost never drops, but most people dont do that since hp is still climbing nicely up before transition despite the boost dropping.

Most people ride the primary turbo out to near its max hp and then transition.

Another issue is the solenoids and actuators for transition dont work well with high boost. This you can solve by putting a simple pressure regulator on the boost line to the sequential system. I put mine on the boost tank behind the alternator.

So there are several reasons your tuner had you set up with lower primary boost.

On BNRs in sequential mode where each tirbo can make much more hp you CAN run higher boost all the way through primary turbo range but it takes some work (such as the pressure regulator to solenoids/actuators).

Some have worked through it and it really rips on the primary turbo.