That is possible and unavoidable. The evaluation of a fully bid hand (see comprehensive explanation) is based on the relative merits of final contracts, but is independent of whether a given bidding system can actually reach those contracts.
So for example, it can happen that the top mark of 10 goes to a final contract of 1NT, while the opening hand has 21 high card points and many bidding systems would want you to open 2NT.
