Yes, it can be done without BB, and without BA, for that matter. But if not using BA then it is convenient to have a sonicator to aid with the dissolution.
What is the objection to the BB, by the way?
The difficulty with using only 1.33 mL of BA and no BB is that the convenience of having all the TA dissolve into solvent first may be lost. (I can't say that positively as I don't do it that way.) 1.33 mL of BA would be very little to dissolve 2.0 g of trenbolone acetate and might be insufficient.
Having another 5.33 mL of BB, giving a final concentration of 20% BB, provides more solvent for the TA to initially dissolve in.