"first of all define what pure is. I would suggest starting with a statement I heard from Dr. David Hill. Pure is 1) only Volatile Aromatic Compounds, 2) the Right Aromatic Molecules, 3)Therapeutic Concentration."
Yes a definition of purity is key. Here that would include your 1,2 with reasonable relation as regards to constituents to British Pharmacopoeia standards (and published collections of GCMS results) which of course are just an average as crops vary.
Obtaining GCMS for every batch is a key control and if it is not available then that speaks volumes.
It is not possible to claim 3. therapeutic concentration for one particular oil as aromatherapists (home user or fee earning professional) rarely use a single oil but blend several oils in recipes (Worwoods are a particularly good guide) for their therapeutic (bodily or psycho-social) effect without one oil necessarily dominating the blend. Oils used on their own often lack therapeutic effect.
The ATC adopt a policy of random testing of members oils so it is not the company making the statement on their label 'PURE ESSENTIAL OIL' it is the industry.
ORGANIC provides further assurance not just of a lack of contaminents but of purity because the oil is traced from farm/distiller to manufacturer by inspection of staff and records and reconciliation of quantities bought and sold.
One day we will get date of distillation but the best by date is not a bad guide to freshness because deterioration of the oil tends to take place in use as the cap is removed and replaced and in storage (is the oil kept refrigerated or not, citrus should be).
Essentia per mutua