A question for you in your pro bono capacity!: the SRD has almost no fiction for races, and pretty limited for monsters. OSRIC has more than what is in the SRD, and it's modelled on AD&D. An example:
Gnoll raiding parties will be led by a leader with 16 HP. He fights as a 3 HD monster.
There are mechanics there, but is that primarily a statement of mechanics, or a fictional statemen about gnoll raiding parties?
It's not mechanics or formulae, no. OTOH a single line like that normally does not have copyright protection in UK law, it doesn't meet the de minimis standard.
Presumably you would say it's derived directly from 1e MM pg 46, paragraph 2: "For every 20 gnolls encountered there will be a leader type with 16 hit points (attacks as a 3 hit dice creature)". It certainly looks like it - NB in 1e a 2 hd and a 3hd creature use the same THAC0-16 attack matrix!
But to make a non-literal copyright infringement claim you have to get lots & lots of stuff like that, so that it's collectively substantial, then extract everything in the SRD, which covers eg the concept of the gnoll, and then establish that what remains is a substantial, though non-literal, copying.
This is a pretty Herculean task - and if you fail you risk a judgement that lessens whatever copyright protection games as games have, with potential severe impact on the value of Hasbro's IP portfolio.