"They know they have PT Bumi's stake in the bag when they make...

"They know they have PT Bumi's stake in the bag when they make the offer, so are perhaps acting conservatively here."

absolutely.

the Bumi stake is simply no use to Petro until they get the recommendation of the Board.
without that recommendation (and acceptance of a bid), any bid goes no where.

so no point in buying Bumi's shares at 42c, if petro gets stuck with the parcel.