Trident seems unobtainable in Survival

Only drowned weilding tridents (can only happen from non-drowned zombies) can drop tridents with the same chances any naturally spawned equipped item drops.

Pre5, I'm using the following:
https://youtu.be/6Skn7VX30HE
I'm killing ridiculous amounts of drowned with tridents in their hands. No trident. While the number of drowned with tridents seems to spawn correctly, actual drops seem VERY painfully rare. Would there be a simple way to verify drop rates? Either our luck is quite horrible, even for using the farm, or something is very wrong in Pre5. 😞

EDIT: I added two drowned spawners within 10 blocks of the villager while my wife held the chunks open. We got lots of drowned in a short time. I then checked the Nether side and I managed to kill lots, watching for drowned with tridents. No trident drops. When I was ready to quit, I saw two with tridents in the gate. I pushed the button to get them out of the gate, killed them, and I got two tridents.

So they ARE spawning with tridents, and once in a great while, tridents do drop. But the rate seems pretty impractical to get a trident without a farm if it's this difficult to get it with the farm.

I would be happy to set up a counter that only counted unique trident drowned within the kill box I could compare against the drop rate. I would be happy to make a series of tests to verify the drop rate simply "rare" and not "ridiculous."

EDIT2: I can make sure the Overworld trap chunks are unloaded and use a spawn egg to drop 25 drowned into the killbox, switch to Survival, then tally tridents. I can continue to do sets of 25 and counting results until we get "about so high", hopefully at least 500 spawn attempts. I'll publish the results here. It should be just as easy for someone else to do the same, even if it's just in a closed off box. I'd be happier knowing other eyeballs and better luck returned some numbers on this problem.