I think face time culture is about being seen to be on the client site.
This could mean one of two things: either the client doesn't trust you to accurately bill hours worked unless they can see you onsite, or that managers want acn folks to be seen on the client site to raise their profile and hopefully generate sell-on opportunities.
The former is more to do with the clients' culture than acns.
Anyway, back to the question of how "Corporate" they are, they have a Company song for goodness sake!
I worked at acn for just over 2 years before they finally broke me. This was largely due to working for Senior Managers and Directors who had no life outside of work, and couldn't understand anyone who didn't want to spend every waking hour in the office. I've since moved on to greener (dot) pastures.