When VW fitted my new engine, it took them ages to get it started.
I saw it in the dashcam.
They run the lift pump for 3mins, made sure fuel was at the filter and up to the HPFP.
Then cranked watching the fuel rail pressure build.
And had a battery charger on the van for good start motor speed.
But they still needed easy start to get it going.
It took 15 odd goes to get it to fire and purge all the air out.