Based on reading this thread, I don’t think we can all come to agreement on who was at fault. But, to me, it is obvious all of us should be considering this accident and develop a plan of what to do if we find ourselves in a situation similar. I was taught if on a collision course, to turn towards the tail of the other airplane. That is what I would have done here. As close as these guys were, and considering the 152 had the 340 in sight, I would try to keep him in sight.
Bingo. That's exactly the way to avoid colliding. In BFM parlance: 1)Lose sight lose the fight. 2) Assess [aspect/range/closure] 3) Maneuver in relation to the bandit(nee traffic).
Good on your CFI for emphasizing the spirit of those axioms. I know this isn't formally addressed in civilian flight training, considering there is zero requirement for formation/rejoin training, let alone turn circle geometry/lift vector management aka BFM.
Keeping the traffic in sight is the most significant piece the 152 left behind on the poker table, and it cost him his life. Out-of-plane maneuvering does not need to conform to rigid civilian preconceptions of pattern ground track and lanes, like some folks tend to latch on/preach. PIC emergency authority allows you to break out of a VFR traffic track in any way that averts a collision.
This wasn't a complicated deconfliction given the 152 had contact against conflict traffic, and assessed closure (at least verbally) correctly. All he had to do is roll out, climb, put lift vector on the 340 high six, and reverse on the opposite side of final at 3/9 crossing. Seems aggressive and overwhelming to the uninitiated, but it really isn't, provided the pilot doesn't go tumbleweed and stall due to lack of a/s crosscheck.
Such a response would offer hundreds of feet of vertical clearance by the time 3/9 line cross between the participants occurred. Putting tail onto the blind traffic and continue to align with final, that was a fatal mistake, and one borne out of not understanding how to maneuver in relation to another aircraft. I don't blame him for that inability; again formation work is not part of civilian primary flight training.
But like I said before, I digress on all that. The answer here for the lowest common denominator is don't cut in front of that which you can't handle, just extend. And if it's that offensive that it puts you 2,3,whatever miles away from runway threshold, just break out and come back on the downwind, no harm no foul.