Z. H. Darkstar
Explorer
One advantage of the Hardcovers however is the Random Encounter tables
Since you can always combine encounters into a super-encounter when it makes sense, there is nothing stopping an AL DM from adding a random encounter, and then combining it with a published encounter. This would give DMs more flexibility to "adding creatures" to an encounter. I wouldn't recommend this tactic except with experienced DMs however - and I would inform players that the encounter was combined with a random encounter (if asked). Last thing I want, is for DMs to be accused of adding creatures to an encounter that wasn't included in the adventure.
I actually did this recently at my OotA table. Since most of the Ch. 2 encounters are weak for a party doing the travel tasks for the Battle of Blingdenstone, I set up a "Day from Hell" for their last day of travel.
The penultimate day ended with them finding the warning sign outside of Neverlight Grove. The ultimate day then kicked off with a battle against Shadow Demons. A few hours after that was the Main Event, an encounter in the Boneyard with 3 Minotaur Skeletons and an interrupting Umber Hulk, as it was also the Umber Hulk's lair.
The trip back was no picnic either. I opted for another 2 encounters in 1 day scenario. The first was a pack of 8 Quaggoth Spore Servants, followed by 4 Carrion Crawlers a few hours later.