Don't think that having entered the chosen program МВА, it's done. The only entrance is not enough. Recruiters, especially during a high rate of unemployment, when hundreds can apply for each vacancy, if not thousand applicants, can demand results of test GMAT before to invite a candidate to interview.  

Yes, results of GMAT can reflect not precisely knowledge of an applicant, but it is well-known, that there is a certain correlation between a result of a person and his abilities, especially in a hard work with figures. Therefore recruiters use it in the same way as  many programs of МВА: for fast elimination of the weakest candidates.

Recruiters consider this fact as a big convenience, after all it allows them to eliminate instantly any resume, after all not reading up it to the end if it has no result of GMAT (and it was required to specify it), or he mismatches certain level. It saves time and money, that is completely perfect with an employer. Even if it means, that recruiters can miss an interview with several tremendous candidates which simply have not so well passed the test, recruiters usually don't like this. A labour market and work search now is very competitive and consequently some recruiters easily demand that result GMAT was not  lower than 700 - in other words, the best 10 % of results from all who passed the test.

Those who take GMAT it is possible to be recommended to repeat it if their result is below 720 points, and they are aimed at very competitive posts - for example, consulting or investment banking. Recruiter does not worry about when the candidate received the best result of GMAT - before receipt on МВА or after. The main thing is that a candidate at least was not worse, and in an ideal variant even is better, than the following resume. Therefore it is important to pass GMAT with the highest possible point.