You need to watch the moisture in your soil. see your woody stems? That is a sign of drought. A plant in a hydro unit, oversized container, or on a drip line will typically never show woody stem growth. This is what the plant does during drought. Why exactly? I don't fucking know, not going to BS you, but you can run your own experiment, you'll know definitively that this is correct information. If your plant ever goes limp, even once, you've done decent damage to your roots. Pull them out of the pot, you'll see some brown stringy roots that look dry from whenever that damage took place, as well as pearly white new roots that grew since you watered again, or started watering consistently. This isn't a big deal during veg and early flower, although it will most certainly slow your plants growth and greatly decrease your plants potential to get as bushy as it could in that time. Roots match the fruits, so if your root zone is cut way back, your plant will never stretch out to match what's going on below. It also greatly decreases the maximum radius your stems can grow too in a certain amount of time.
Here is where it gets really fucky when your plants experience drought: flowering. between the 3rd-5th week of flower your plant stops growing roots. If you damage your roots with dry soil, they will never grow back until reveg. This means if you have a plant that grew to full size, and then half the roots die off, your rhizosphere can only supply 50% of what your flowers above require. You'll get massively reduced yields, and your plant will be highly susceptible to further drought, high/low temps, high/low humidity, fungus, and pests. If you're deep in flowering and your plant goes limp once, you've pretty much shot yourself in the foot. Sure you can get it to harvest with high quality flowers, but you'll find you have to water twice as much to keep it from happening again, or in a worst case scenario, the damage is so bad your plants take twice as long to drink water, and have a difficult time metabolizing, resulting in a low yield of low quality flower.
Right now, you can easily pull out of this and avoid all these issues later in your plants life. As they are now, they probably would have no defense against a pest infestation, so you may not be able to boast about never losing a plant for long. If your plants have never dried out, never gone limp, and this is caused by something else, please inform me, that would be very interesting information to look into.
Also, that is not going to be a 20 lb plant. I'd believe 10, I'd believe 12, I might have to see evidence if it were to be 15, but 20? No way. That plant would rip itself to shreds under the weight of all those flowers. It's hemp, not timber, it peels apart like string cheese. If you only get 10% of your wet weight, that means those branches would have to support 200lbs of fruit. No way. Not without an extensive system of branch support, and definitely not on a plant of that size without abusing PGR, Plant Growth Regulators, which are potentially dangerous to your health. Not to mention with that dense of foliage you'd loose a lot of weight to fungus, unless you are in a micro-climate that doesn't support certain fungus, or rely heavily on toxic fungicides like Eagle-20.
That's just my two-cents. more like two bucks with how much I typed out, lol.
I should mention that large outdoor plants often get woody stems, but that is because they are frequently busting and healing from rapid growth. I just don't think what I've seen of your plants would cause that, they aren't under intense lighting or wind, and they don't look exceptionally vigorous. Not saying that the leaves don't look healthy, they do, but I still see stress.