Yes, it is about attack - the type of attacks that one intends in a competition. So, it has more to do with competitions that O Sensei detested later in his life. In this sense, I need not mention the name of the senior disciple who was "ex-communicated".
Go-no-sen, sen-no-sen and sen-sen-no-sen are fighting/competition strategies/concepts. I first come across these terminologies in kumite (karate competition) training. These concepts are also used in kendo and judo training. Without dwelling into details, in karate competitions, one scope points by landing blows/kicks to specific areas on the opponent's torso or a near/close contact to the head. When faced with an opponent who has a defensive posture and has these target points well guarded, then, one may need to apply tactical measures to bring down the opponent's guard - this may involve feints or presenting an opening to entice the opponent to initiate an attack . Hence, techniques can be categorized (but not exclusive) as Go-no-sen, sen-no-sen or sen-sen-no-sen depending ones intend. In the old old days of sword fighting in Japan, a duel to the death could last hours with the opponents facing each other in guarded stance/posture. Like a game of chess, each knew the game and the strategies awaiting for the wrong move would result in fatality of one.
This maxim from Gichin Funakoshi applies aptly to our jiyu-waza as it would to karate-do: "Create an opening and you would find the technique". With this, I leave it to you to figure out what he meant