That is not correct. A transmission that behaves this way is faulty or misadjusted. When they're in good condition and adjusted correctly, flooring the accelerator in 2nd gear below a certain road speed (determined by rear axle ratio and tire size) kicks the trans down to 1st, doing it in 3rd gear below a certain speed kicks down to 1st, above that speed kicks down to 2nd, and above another (very high) threshold speed doesn't kick down at all.
What the pre-'68 (6-cylinder A904) pre-69 (V8 A904) pre-70 (A727) transmissions don't have is
part-throttle downshift, that is the ability to go from 3-2 with the application of just
more accelerator, not a kick to the floor.
Rod-operated kickdown linkage on all the Torqueflites clear on up through the end of the M-body cars (last ones in '89), trucks and vans some years after that. In the mid-'90s they switched to a kickdown cable. Lokar, I've never messed with -- too many accounts of too many people having too many problems making it work right. Factory cable-type parts can be adapted to work nicely; see
this thread for kickdown options.
ATF+4 fluid won't cause problems that don't already exist. Dexron-VI is a markedly superior fluid (references/data on request)