This has been discussed a few times.
Angling the bar does indeed line up the bar with the grain theoretically making for an easier cut but it also makes the cut longer so the two effects usually cancel each other out until you reach really high angles requiring the bar to be nearly as long as the log..
For example even with the bar at 45º you are still cutting half cross grain and half noodle,s but the length of the cut is now some 40% longer than straight across the log.
If you are not convinced try timing cuts.
The belief that this might help comes about because (especially newbie) CSMers often start a cut at an angle and feel how easy it is (remember its not cutting as much wood) but before they reach full cut width seesaw the bar the other way so they never mill across the log at full width.
This seesawing is not usually faster and can also lead to a poorer finish because the seesawing effect slightly twists the mill in its frame and will produce an uneven finish.
There are a few times when I do seesaw towards the end of a long wide cut, not for speed but to take some load of the powerhead as the chain gets blunt.
In terms of finish, it's usually better to stick to one angle and apply firm constant pressure all the way down the log. If possible I don't even stop add wedges etc which s why I use the log rails for every cut - then the wedges and hammer can sit on top of the previous cut and the mill slides over them because its on rails.