It is quite possible to have an expanded or even exploded cap -- if there is enough amp spike through your system. A bad motor or sensor can do that. The cap can to some extent protect the esc - but its not a guarantee.

Its also possible for a cap to provide a little extra "punch" when discharged, calling it "dirty" or not, any energy stored and then released (even though its a very short time), can be a technical help.

But there are more ways to lose a .1 of a second than there are to gain a .1 of a second.