Another thing I must explain is many hardwood pellets are generally a mix(blend) of different hardwood species. They except the wood from different sources and blend them together to make the batch for the run. If there is more of this(say oak) than that(say maple) this time and more of that than this next time you get a variance(hope you followed that). Same goes for softwood which is a mix of SPF. A pellet made with mostly spruce will be a bit different than a pellet made of mostly pine. Blend pellets(hard-soft mix) could also have variance like this as well
Not many brands use a single species to make pellets. Turman's and Somersets are flooring companies that use 100% oak to mill flooring. The dust and chips left over go into our pellets. There are a few softwoods that are a single species(Ponderosa pine and Douglas fir). And mills that produce pellets from there own mills can control the mix/batch a bit better than the mills that except fiber from the open market. Mills that control their fiber in house generally have the most consistent pellets going.
Log to chip pellets are something new in the past few seasons. Fiber shortages and low construction trades have reduce the available fiber. So some mills added whole logs to their process. Logs must be debarked, Chipped and hammer milled down to workable fiber sizes to mill our pellets. Not getting all the bark off will hurt these. Geneva and Maine Choice are log to chip pellets.
Heck even the soil that a tree grows in can effect the fiber it produces. Minerals it collects during growth is one factor.
I have only touched the surface, I wish one of the pellet pro's could drop in and add some things. Its almost like secrets they fear to share. A lot I had to grasp on my own. Sure hope I got most of it right!