I have worked with @larsentoubro for 2 yrs.

Have also interacted with Mr S N Subrahmanyam few times then in 2015.

Working Saturday was always irritating and taxing for me as well

But, his 90 hr workweek comment is in exact sync with what his company requires.

Let me give the context 

Imagine that L&T is building the metro in your city.
If L&T works during the night, your metro will get built in half the time. 
This means metro functional in 5 yrs Vs 10 yrs - BIG difference 

Also, L&T is a hierarchical organisation like the army.
Discipline and work ethics are way more important than knowledge /brilliance / creativity.

For educated, middle class, non-software engineers, @larsentoubro is one of the best places to work for life.