Not necessarily. With only 8 teams in the conference, you had to play everybody instead of only half the conference now. You still play a similar number of total conference and out of conference games as you do now. If it was more difficult to go through the season undefeated, we would see more teams finish the regular season with at least 1 loss. That wasn't the case with 3 teams finishing the regular season undefeated this year.
Playing everyone in the league is irrelevant. Also, no one was talking about finishing the regular season undefeated. They were surprised the Saban has only had one undefeated season total.
From 1970 to 1991, when the bowls had tie ins and there was no attempt to match the top 2 teams, in 22 years there was 17 undefeated teams.
In the 3 years of the Bowl Coalition, 1992-1994, there were 4 undefeated teams in those 3 years.
In the 3 years of the Bowl Alliance, 1995-1997, there were 3 undefeated teams in those 3 years.
In 16 years of the BCS, 1998-2013, there were 12 undefeated teams in those 16 years.
In the 5 years of the CFP, there has been 1 undefeated team, Clemson this year.
Since 2005, when Texas beat USC, 14 years there have been 6 P5 teams that finished the season undefeated.
If we are talking about undefeated regular seasons, Saban has had 4 since 2008.