"Your compost killed my 100 year old tree!"
Whether it is was true or not (not too likely) that situation would still SUCK.....
Ask for an analysis sheet from them. They should have a certified lab test sheet. You might want one on record, just in case someone tries to make a claim against you. As well as being able to use for marketing/education purposes.
And also take note to see their inputs.
For example at my local county landfill they separate the yard waste. It gets ground, screened, and then is used for various purposes. Would I want to use it? No, because ANYONE can dump a load of greens into the "compost pile". Any load! Maybe a load of grass heavily laced with Roundup. Or maybe there is a container of chemical in the load of leaves that gets scooped out and gets crushed in the pile to spill its contents before it is screened out. Or there might be plastics in it, etc. There is no quality control on the inputs.
Whereas the egg farm is very consistent. It's chicken waste and the input is the same 365/24/7. An occasional dead chicken does meet the pile, but that increase the bone meal & feather meal. So the variance is positive not negative.
In other words, what level of control does your supplier have on the input?
And what is the consistency of the product. If the fall compost is mostly leaves, and the summer compost is mostly grass and branch clippings you will have different results. Not necessarily bad, but different.
The other side is-- compost is relatively neutral. It's not like pouring on liquid urea, so even if you get a bad batch it is not likely to do major damage. Although I am sure there are some 'good' stories out there.