Yes. Asking the question means you are doing something dangerous without understanding how to stay safe, and having to rely on unknown, self-appointed internet experts to literally stay alive. Its no fun to be told that but paralleling packs shouldn't be done at all unless you are pretty well grounded in the subject already.
The right situation: have two battery packs that are exactly the same. The same cells inside, preferably from the same production batch, with the same BMS' and even the same charge cycle count on both packs. The use of a battery blender is supposed to render you immune to the problems that can occur with not doing these things. You get to decide if the Far Eastern vendor, who has no product liability, is committed to quality and even knows what they are doing in the first place.
EDIT: A short, honest and direct answer to your original question is "nobody knows" because these blenders are made by different vendors and they behave differently. Only someone who has intimate knowledge of an individual product can speak to the subject, and their answer is worthless if you jump over to a different product made by a different vendor.
