JR,
Yes, in answer to your example question; recoil will be the same even though the pressures are quite different. Pressure has no bearing on recoil and because of that it is absent from the formula for calculating recoil.
Excessive pressure can & will, however, have a decided effect on how quickly a doublegun may become 'off-face' or loose due to added stress factors beyond intended design limits.
Both pressure and recoil are important factors that should be taken into consideration in selecting suitable ammunition for a given doublegun, but they are separate and distinct and must not be construed as similar. They are not. Either, when excessive, can contribute to premature or even catastrophic failure and unnecessary wear & tear.
Best, tw
