I agree with you 100%, in my opinion this is a direct violation of 240.8 as you pointed out.
240.8 Fuses or Circuit Breakers in Parallel.
Fuses and circuit breakers shall be permitted to be connected in parallel where they are factory assembled in parallel and listed as a unit. Individual fuses, circuit breakers, or combinations thereof shall not otherwise be connected in parallel.
There could also be another violation.
240.4 Protection of Conductors.
Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).
Two 150 amp breakers in parallel will provide 300 amps of current.
Are the conductors rated for 300 amps?
Is there any chance this engineer is from Europe?
