From a quick search, ethylene (C2H6, not C2H2, btw) is worth ~$700 per ton. If the researchers could re-tune their process to produce high-quality ethylene, that's fine. (Within limits - the potential market for ethylene is probably far smaller than that for methane.)
For on-site "methane battery" uses, it's probably fine if your methane is fairly contaminated with a known-when-you-designed-the-system mess of somewhat-higher hydrocarbons.
But from a quick search, gas and power utilities seem very much concerned with higher hydrocarbons in their methane. And "higher" = "worse". Which makes sense. Those would alter the proper fuel/air ratios, and probably impact emissions. And they do not want liquid hydrocarbons to condense inside their high-pressure gas lines in cold weather, then cause "water hammer" damage to equipment.
Ethylene, on the other hand, is a chemical feedstock used for many products. There's been a longstanding effort to upgrade methane to ethylene because the latter is so much more valuable.