In those 3 partial seasons you mentioned, his PPG was 1.61. Excluding those, his career pace is 1.24 PPG. That's why it is unrealistic to think he would have been able to keep up that pace. He's never done that over a full season.
He may still have achieved the PPG those seasons but without playing a full season, you just never know. Maybe he'd be more like the 4 year run from 2014-2018 where he averaged 1.10 PPG
Even if he scored at 1.10 PPG for the rest of those seasons, he would still easily have had more than 1 PPG. Like very easily.
Using career pace is also a little dumb here. Players of Sid's caliber usually have their scoring peak around 22-24. His performance in 2010-13 aligns with that (23-25 instead of 22-24, but close enough). His peak was an outlier, sure, but it is for all players.
I do not want to make it a Sid vs Ovy comparison, but look at AO's 3-year point scoring peak (which is age 22-24, btw):
2007-08: 82 GP, 112 points, 1.37 PPG
2008-09: 79 GP, 110 points, 1.39 PPG
2009-10: 72 GP, 109 points, 1.51 PPG
TOTAL: 233 GP, 331 points, 1.42 PPG
So, during his 3-year point scoring peak, he scored at 1.42 PPG. His career PPG is 1.11. His 3-year peak is 27.93% over his career average.
Let's look at Sid now.
2010-11: 41 GP, 66 points, 1.61
2011-12: 22 GP, 37 points, 1.68
2012-13: 36 GP, 56 points, 1.55
TOTAL: 99 GP, 159 points, 1.61
So, during his 3-year point scoring peak, he scored at 1.61 PPG. His career PPG is 1.27. His 3-year peak is 26.77% over his career average. That's remarkedly close to Ovechkin's deviation, isn't it?
Season before that peak in PPG, Crosby scored 109 in 81 (1.35). Season after, he scored 104 in 80 (1.30).
Based on the data, there is absolutely no reason to think he would have dipped under 1 PPG for any of the seasons in which he missed a lot of game. His deviation matches his closest peer. He had a very good pace the season before and the season after. His career LOW is 1.06 in a season in which he finished 3rd in scoring.
His career low is a 16.35% deviation from his career average. For comparison's sake, Ovechkin's lowest PPG season is 0.83 PPG which is a 25.23% deviation from his career average. So Crosby's worst year deviated less than his closest peer's worst season. Heck, if you want to argue that Sid is more consistent, while Ovechkin's deviation for his best and worst is more volatile and say that Crosby would probably have regressed to like 1.45 PPG (14.17% deviation from career average, which is more aligned with his deviation from average to worse)... he still VERY easily scores more than 1 PPG
If people were to argue that he would have broken 150 all these years, games missed and difficult to sustain pace would be good arguments. When it comes to consecutive PPG seasons? Nah, that's just arguing in bad faith.