There are certain aspects of crafting that is random, and others which you can have control over.
Such as look at the EXP earned for completing the craft for the mahogany lumber in the OP; 759~764. You have no control over that. You can find your own examples as well when completing any craft to compare EXP results, sometimes the variance is much larger than 5xp for completed synths.

You do have control over the success rate depending on the tools, stats, and choices you make during the synth. This should be indisputable. Such as if you keep spamming standard synth your chances of failing a synth out of your level range is higher oppose to carefully picking your choices and observing the changes.

I personally take the easier route and earn 300 EXP per synth by just mashing Standard Synth rather than spend twice the amount of time and actions to carefully monitor color, sound, and my available choices at the moment. It was fun to do the first few synths to see if it's possible, but now I just spend that time multitasking something else while just hitting the enter button occasionally.