TPS7A91: MSL Package Type - MSL 2

Tool/software:

Hi Experts , 

Good day , 

Just a general technical QA query . Refer to below image of MBB package of MSL 2 component ? Is it mandatory that MBB package should be airtight or sealed package is enough to protect the parts from Humidity environment as per TI std ? 

I have a package where there is no airtight one and it was sealed one . 

Pls advise 

Thank you 

Regards 

Manoj Balakrishnan.