Transplanting Bird of Paradise

I have an old BP that has made beaucoup pups over the years. I wanted to transplant it -- them -- to create a privacy screen between me and neighbor (where I had huge hedge removed).
My wonderful landscape guy -- not regular gardener -- nixes the idea. He says it is too warm to move a BP now. Something about the roots extending way out; they would have to be cut; the BP won't like that because the roots contains water, which will "leak" out and the BP will not transplant well. Advises waiting until Nov. or Dec.
Now I have to regroup in a hurry, as I was counting on those BP so I wouldn't have to buy big tall plants.
QUESTION: Anybody have experience with transplanting big BP? Can you bear out his opinion about too warm now?
Would appreciate feedback.
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