That's just saying "we push our memory problems up the stack so our clients / users need to deal with that". The reason this works is because human users in particular have become accustomed to software being buggy and failing often.
No, it does not. The oom killer acts on (mostly) the oom score and no process is exepmt, regardless of whether or not it allocates new memory.
It may help you write correct programs in certain situations though, eg. if your program was running in a defined context, eg. a cgroup, and you would not allocate beyond your cgroup limits, and the system was configured sanely, you can handle allocation problems easier.