It was just my first google result for "methane co2 equivalent", and so the number came from this link (am Australian) - https://www.cleanenergyregulator.gov.au/NGER/About-the-Natio...

You are right that there are different valid factors to consider, as can be seen here: https://en.wikipedia.org/wiki/Global_warming_potential

But also, 25x vs 100x is a 4x difference, which doesn't affect the comparison to coal that much (it's still single digit % "at best").