First of all Yoshida and Crew are the same since 6 years. Only Yoshida got promoted and Tanaka, well. Yoshida is always writing, that it is so complicated to change things and if the hardcode would be lost, this game can be closed now.
But in my opinion SE didn't programmed many things for themselves. They hired people to write a RNG generator for example. For low budget game studios this is common and i think the crew is working just with an construction kit with modules integrated. We call it White Crystal engine nowadays. These modules are the main problem.
YoshiP is a simple manager. Do you know what this means? He hasn't programmed or constructed anything. Maybe he is even not able to. He is just planing and coordinating.
Back to the problem. I also think, that his crew is too small. Most members are probably gamedesigners. Making textures and writing event scripts with the construction kit. There is this one battledesigner, we have heard of lately. And i doubt, that he even hardcode anything.
As you probably see for yourself. The knowledge of the gameengine is limited to a few people, which can hardcode and improve things. There are definetely modules like every gameengine has, that needs to be rewritten from scratch.
Those few people are to 99% not FFXIV Team members. The white crystal engine is used in many games and therefor it must be a special team or a team that even doesn't exist anymore. If SE uses 3rd party programmers for modules, it is even worse.

Topic random SP: If you really think SP shouldn't be "random" and you want the exact formula: OK.
But in my opinion you want just plain SP, no difficulty, not anything else.
"That is a lot of random things that we have no control over you have listed there... meaning it still randomly gained SP, even if all that were true, which it probably isn't."
No offence, but don't you think, you are a bit limited? I gave you a formula, but it is not enough.
You want total control over something, that is called a minigame. It is intended to vary.
If i go a step ahead, i would say, you want to skip this minigame and just pressing a key and there it is, your synth, like FFXI was.
Sure we want to know the basics of crafting like the thread starter. We have never seen an explanation in FFXI and we will never seen an exlpanation in FFXIV. That's the way YoshiP is doing it. He is the lead manager of both games. We can speculate like i did above, that most likely only one person has a clue about the synthing formula. But in the end it doesn't matter.

In my opinion the variety is so small. See the thread starters numbers. At higher difficulty synths, the variety is more evident, because the base SP is higher and so far every multiplicator has a bigger impact. But even then, you have an average SP output, that sums up for all of us to the same SP.
See my formula: all your synthing progress in total/number of steps = mean value.
We are all able to predict the total SP gained after 100 synths. And if you don't fail miserably, you can buy your items in advance to reach just a specific rank. I have done this many times.

FFXIV is like Linux. Everyone is programming on something. They make stupid mistakes on their own. They are independent developers and don't know, what other have done. More errors are following because of the combination. At the end, they compile against a kernel, which only a few people know about exactly. Someone announced the mixed up garbage as a stable operating system, although it's not.
Guess, who this someone could be for FFXIV?