High-purity methane is much more valuable than methane with a grab-bag of larger hydrocarbons as contaminants.

Especially if said contaminants include stuff like H2C2. That can be rather explosive. And might accumulate somewhere in the plumbing, unsuspected until ...

What's the market for that? The vast majority of users of methane don't care much if it has some higher hydrocarbons. The methane ends up burned or reformed anyway.

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.

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.