If that stat meant anything, I'm sure Pep "I'm in love with possession" Guardiola would have found a way to use him and not put him up for sale.
Of course the stat means little just like nearly any other stat without context. The biggest reason, why Gustavo won´t have much of a future at Bayern is of strategic nature. Guardiola simply prefers a system with just one true DM/CM and Gustavo is not suited for that. For that particular role he is indeed not well rounded enough. That does not say much, because it is one of the most demanding roles in modern football and at this moment I only see Schweinsteiger really excelling there (maybe Martinez proves me wrong in the future here).
At the danger for some people jumping on me for having that opinion, I still attest Gustavo a good passing game. I know that we disagreed on this matter before, which comes in my eyes mostly down to rating his approach of passing differently. Gustavo has foremost a devensive approach. Most of his passes are indeed safety passes, taking little risks and making sure to keep possesion instead of driving the game forward with more vertical play. I know and can understand, why this approach is not the most beloved and rated one, but I still think that it can be very valuable in a lot situations. I think the best way to describe his passing is simple, but very solid.
There is actually not that much to say about Gustavo, because he is a very straight forward player. You know exactly what you get with him.
To put it simply, he is an old fashioned destroyer, having nearly exclusively defensive strengths: strong tackling, excellent anticipation and positioning, high work rate and solid passing. Apart from his occasional long range shooting he is hardly spectacular. He is the kind of player, where you really see his worth when he is not on the pitch. What he does not is, is a creative play maker. He does not have magic in his feet and constantly busts out breath taking key passes or provides the main drive of the offensive. He is at his best at giving defensive cover to a creative midfielder, so that the latter has the room to do his magic.
Now, the most important question is, if United has a big need for a player from the mold of Gustavo. Some might argue, that he would not be productive enough, which is fair enough, but looking back at the last season, I don´t think that the problem of United´s midfield was productivity. A fair amount of chances were created there from Carrick (despite shouldering most of the defensive responsibility alone) and Cleverley (decent in that regard). The biggest problem was IMO stability. The midfield was simply far too often overrun, because Carrick was left alone and had to cover a huge amount of area, which was simply not possible.
In that regard Gustavo would be worth gold. He would close gaps and spaces very effectively and provide a lot of stability. I also think, that he would not only be effective against stronger sides, where United has less possesion, but also vs. smaller counter based sides, because he is very good at playing against counters due to his strong anticipation. He has shown in the past, that he can make crucial interceptions and diffuse dangerous situations before they really occure.
In terms of offensive needs, he would need a creative partner, though. I have no doubts that Carrick could fulfill this role, if he is given enough cover and freedom to do so. I also believe, that Cleverley could grow in the role of an offensive CM, if given such solid back up on the pitch.
All in all, I think Gustavo would be a good signing, especially for that price. He is not the answer to all of United´s problems in the midfield, but would certainly answer a good amount of them.