You really need to look at the gust envelope and compare Va (design maneuvering speed), Vc (design cruise speed) and Vd (design dive speed). All 3 are combined with certain gust inputs of 2 different levels.
V-n diagram (gust envelope)
In turbulence it is clear you need to reduce speed as the biggest (regulatory defined) gust can overstress the aircraft. This is the case ie for Vc (and Vd). In the diagram you need to look at the Vc gust line, between the stall speed curve (with increasing g-load this is more commonly known as "accelerated stall") and the +n maneuver line (fixed structural g-load ie 2,5g). Between those two points is your "region of choice" for the turbulent penetration speed. ALthough you better keep it below Va to avoid overstressed pilots trying to recover and overstressing the airframe themselves (something like that...).
Of course there are many weights to take into consideration, but to make life easy there is one speed defined that sits on that line and works all around for different weights. It is fairly logical to state that with reducing weight, the ("accelerated") stall curve will move left and allow lower speeds. In the case of the B737, Boeing has tested and verified these margins and published the 250kts below MLW in the manuals. If your manufacturer has not stated this, this doesn't mean reducing speed is dangerous and you risk a higher-g-load stall, however, the manufacturer has not verified this and does not take responsibility for it.
For all these reasons the recommended approach is to fly attitudes starting from a recommended penetration speed: speed excursions are possible but if you've started at the penetration speed you should be protected against accelerated stall, you should be protected from structural overloads, and still retain some controllability (but don't exagerate as you might still "stall-it-out")
Anyway, it's been +20 years since engineering and I split paths, hard to imagine I once found this logical... feel free to add/correct/ban
PS as a frame of reference: if you've ever done a +2g landing, that's the turbulence level you're looking at... (according to the books: "can't read instruments" aka "can't read speed" aka if you manage to grab the button on the first try it's not enough intensity...)