I guess writers just tried to give a closure to s8 theory or the whole "sam hit a dog "thing...dean as well as audience was kinda given a closure about the whole storyline coz its still considered the worst thing he did so yeah it was like assuring audience i guess about dean,not angry with sam,n sam did mouthed his feeling...
The issue needed to be solved so they did it this way...regarding luci saying it to manipulate sam...i guess it will help him coming in terms with that amelia storyline
...like atleast sam knows now that dean has forgiven him and he dont need to see that s8 doings as a burden on his heart???
Regarding s9...sam said words in hurry but he did knew sumwhere he went over the board...though he realised it later but it was too late i guess...i understand his anger on dean..i understand his need to yell at dean or even break a few bones but still i think the i wont save u if u r dying stuff was huge...atleast acc to dean pov...so,the whole stuff did take a toll on dean n at end sam felt guilt coz he blved he let down,his bro...which was a bit true to thw season..besides they were hostile for most of the season with each other...
Regarding s10...like i said..he blved to let down dean n he wanted to be what dean had been to him...so all in all his guilt pushed him further to take matters in his hands and woah...he did made some drastic decisions n boom darkness ia here..n he blames himslef...i dont think his accepting his fault makes him any less...it just pushes him to make it correct which is a good thing...regarding luci telling him again n again what he has done...its all just to manipulate him...to use sam to say yes...
Luci knows how messed up sam is or im general both bros are..he knows where to hit to push them...
Dont remember what charlie said...will get back to it when will watch...
I guess sam povs rnt much shown...in these last two three seasons usi ki bharpayi ho rahi hai is season me...that sam,is opening up to dean..
They never showed sam feeling bad for not searching dean,they never showed any emotion later when sam said the whole s9 controversial lines...s10 was a disaster...so all in all...they did showed him angry in s8/9n then guilt ridden,in s10 ...n noe in s11,he is actually doing theryt thing but then how come they let winchesters om same page...carver ka angst drama n boom...cass says yes,dean never says his feeling to sam...