There's a big difference. There are load carrying boards built into that tank. Notice that they've got a board on each end of that support piece running down to the bottom of the stand. That means there isn't anywhere for that support piece to go. It's not going to bow in the middle.
In your current design the only things taking the weight of your tank are the screws connecting your support to the frame. There's not a lot of wood in those 1" pieces to hold those screws when they'll have all that weight on them. I'll bet if you pushed real hard on those boards you'd hear them cracking.
You'll be fine if you put some blocks under those boards. I'd put one on each end and probably two in the middle, just because. You could probably get away with one support in the middle, but why risk it.