Good question. I do not have experience in coal-bed production. I’d be willing to be enlightened.
To my knowledge, coal beds may be recognized as transitioning from moss>peat moss>soft coal>hard coal>low-sulfur coal (PRB?). The presence of methane in any of these is an engineering estimate. While some moss/coal-beds have exhibited evidence of “fossils”, the overall mechanism appears to be temp/press influences within the crust, not specific to “decayed life forms”.
Do you posit that coal beds are a precursor to O&G, given enough time? The argument against that is the O&G production in North Africa...there are no massive attendant coal beds. Qatar? Yemen? Iran?
Given my limited knowledge, I’d posit that there are several tectonic influences in creating the large instances of moss/peat-moss/coal beds throughout the world. It does not equivocate to O&G deposits.
As an aside, the reason why the source rocks in many basins produce mostly gas and very little oil is that they are Type III kerogens, which is derived from terrestrial plants. Think of a big flood in the Mississippi River carrying all the plant debris out into the Gulf where it sinks to the bottom. Oil source rocks primarily are Type II kerogens while some freshwater lakes in the past in the Rockies areas for example have produced Type I kerogens, which has their own distinctive types of crude oils that result from them. I believe they tend to be very waxy.