Question about Democratic National Convention roll call procedure

I wasn't sure if this should go here or GDP, but I decided here because it relates to something that happened 8 years ago.

Just for fun, I decided to rewatch the 2008 convention roll call (because I'm a nerd, and love that stuff, plus I will never get tired of watching Obama win). I noticed that the first few states cast their delegates in proportion to the primary results, but then Arkansas, presumably at Clinton's request, cast all of its delegates for Obama despite Clinton winning over 70% in the primary. Doesn't this violate convention rules? I thought pledged delegates had to vote based on the primaries on the first ballot, then were free to switch on subsequent ballots if it came to that.