That sponson on the port side forward is clearly only about 2 decks high. However, the top side of the sponson is set only minimally below the level of the flight deck, meaning whatever you put on the top side of the sponson (like an Type 1130) will possibly stick up obtrusively past the floor of the flight deck, possibly interfering with flight ops such as by risking contact with rotating helo bladdes, UNLESS whatever equipment gets loaded onto the sponson, is flush or nearly flush with the level of the flight deck....
The other possibility that I just thought of is that the sponson actually has a solid rail already installed around the top side of the sponson, and the sponson is actually even less than 2 decks thick.