No, I wouldn't concur with this, treez.
There are many SMPSs of this power level range that pass radiated emissions without a metal case, many power bricks for a start, some use no screening, some use selective insulated copper foil screening in a plastic case.
There are many variables - the quality of your main PCB layout, routing, and suppression components, Y caps placement etc., whether you are using a 3 wire mains lead (whether the metal shielded box would be low impedance earthed or not), radiated emissions from input and output leads etc. It is down to how well you integrate this oem module into your product and characterise it.
I remember this being explained to you several times under your various identities.