Thatās not really correct.
And there are lots of different types of locks. In most conversions there will be something like a yale rim lock and a mortice deadlock. The deadlock will not be able to be opened from the inside without a key if it is locked.
Three-point locks have a lock that will only open from the outside if you have a key, and will open from the inside without a key, but there will also be a second, deadbolt lock, that will require a key no matter which side you are on.