Not sure what's going on here..... Booster 16 is/was planned for test flight 10 in the next couple of weeks. Unless it's just temporarily parked prior to moving to the OLM once the hold down clamps are reinstalled and they need the megabit for the next booster build.
Booster currently in the Megabit is Booster 18 - the first of the block 3 boosters. Block 3has an integrated hot stage forward dome eliminating the need for a separate ring to be installed before launch, as well as the requirement to jettison and expend the hot-stage ring. With this design change, the grid fins will no longer be located in the interstage, as with current boosters or Falcon 9, but rather in the Liquid Methane (LCH4) tank.
Along with the grid fins moving there are now only three instead of four, and they are spaced in a T shape, with a fin on the port and starboard sides, and then one on the non-tower side or the heat shield side of the ship so that all the grid fins are in the airflow during glide back and descent.
The aft section of the booster is where things change. block 3 uses Raptor 3 engines and has just two booster quick disconnects, one for LOX and the other for LCH4, along with other commodities. This also helps eliminate individual Raptor 2 engine Quick Disconnects, which have been a challenge for SpaceX to refurbish on the current Launch Mount design.
Block 3 are planned to use launch pad B, not sure when that will be ready for use - but booster 16 was planned to be the last block 2 to use launch pad A.
Booster 16 has moved to the Starbase rocket garden joining Booster 17, Booster 12 and Starship 20.
