Why does insurance take so long?

In July 2021 my husband received a promotion that included 100% family paid healthcare premiums so we (2 adults, 2 children) switched from my employer plan to his (BCBS IL). The informational materials on his plan information say that the coverage period is 9/1/21-8/31/22. However when reviewing the EOBs it states the benefit period is 1/1/22-12/31/22.

It is a PPO with deductibles of $750/$1500 and OOP Max $3400/$6800.

I have called several times trying to determine how the dates are different, why, and how that effects the plan and most people I have talked to are as confused as I am. We are normally healthy, low insurance users however at least 1 family member has met their OOP max last Dec and then again this August. Anticipating another 1-2 meeting OOP in September and Dec/Jan. This means we could be paying significantly more than needed depending on the plan dates.

Also of note, the spending section of the insurance website is inaccurate (deductible spent is stated as less than OOP max, or carried over from previous year, deductible not counting toward OOP max, previous years incorrect). As of Sep 1, the new OOP max took effect (increase of $400 per person but still showing our previous amounts spent).

Has anyone ever heard of having a different coverage period and benefit period? Is there a way to ask for a higher level review? How can an OOP spent be less than the deductible spent?