When recording a real orchestra, unless isolated in separate booths or recorded in several sections, you will basically hear every instrument on every microphone. This goes particularly for loud instruments like percussion and brass in forte or above. Even separation by acoustic walls in the studio will only help to a certain extent. This effect has advantages and disadvantages.
The advantages are that with this microphone spill, in the mix you will get a very homogenous sound and it is easier to create the feeling of an ensemble playing together. Also you get a considerable push in the perceived size of the orchestra through all that spill with small and medium sized orchestras sounding quite impressive and big orchestras sounding really massive. So with a well orchestrated and balanced piece, you can get a really “orchestral” result through this. There is a limitation to this in some special cases, described below.
The downsides are the lack of possibility to alter levels internally. The microphone spill will only allow you to adjust individual levels in a very narrow corridor before sounding artificial or standing out. So if the recording is unbalanced, there is little chance of fixing that it the mix. Another big downside comes with any percussion that is loud and keeps playing through the piece (e.g. big trailer music percussion grooves). The spill of these percussions on every mic (which they most likely will do due to being much louder than the rest of the orchestra) makes it very tricky to impossible to give them any punch in the mix as different distances to the sound source and therefore different signal running times will blur all transients and weaken the punch.
An often used solution on this is to record the percussion or other sections separately from the rest which helps on this end but creates two other problems:
1. Stripping down the arrangement makes it trickier for the musicians to find their role in the music and the overall sound which will result usually in a weaker performance compared to them all playing together
2. When recording the same “room” several times and layering that on top of each other, the ambience will sum up differently than if they played together and in extreme cases create a lot of mud in the mix.
So you always need to weigh these factors against each other before you record in order to create the best possible result.