This experience is a big favour, and an honour - it is a privilege to sample their new spirit, with added water (typically). It gives a deep insight to the very soul of the whisky they make, and makes for a great reference point to tasting their more mature products.
Every new make is unique in taste: The maltiness, the grain and barley, the floral aspects, the fruit,smoke, spirit, etc varies in fabulously complex ways, but also maps a connection to the mature spirits.
As we often find ourselves speaking of how much added sweetness rum contains, whilst producers generally either decline to comment, or claim it isn't so, I wonder how many of them actually would be willing to offer rum writers and connoisseurs a sample of their new make straight from the stills to taste?
If the new make is not sweet, it must be God's miracle if the mature spirit has by some divine effect become sweet as aspartame...! That's a miracle almost as good as turning water into wine!!
We pretty much know what cask maturation does to spirit. We know what different types of casks do to the spirit. None of them make a spirit sugar-sweet. That's why whisky isn't sweet. That's why Bourbon is not sugary-sweet either. Yes, there is vanilla, and ex-sherry adds raisiny notes, sometimes meaty BBQ, leather etc. But none of the ordinarily used casks make a spirit sweet as yack..! So the big (no brainer) question is - why is almost all commercial rum sweet? Guess...
Vodka producers start with a spirit quite similar to modern rum column still makers, i.e. pure, "high-voltage" alcohol. Every vodka maker I've spoken to say that yes, they distill as pure as they can, and then they "make the product", i.e. filter it, add sugar to it, etc. to make it more palatable. They do not hide this. I guess rum is one of the few spirits sadly where facts are still hidden from public in a draconian way. That is just ignorant, if you ask me.
