I think the filter did what it was supposed to do, and you have to keep in mind that collected all of the contaminants that were in the system from manufacturing, which includes grease, iron filings, casting grime, etc.... There is a cumulative effect. I bet that a sample taken from the fill cap with a turkey baster (or just suck out some with a clear tube) will look 1000% cleaner. I would not use any fluid from the filter (or any filter) for an analysis or even to draw general conclusions.
Heck, if I look at a used 90-day air filter on my HVAC unit, I could stretch the facts to make it look like we have a dust problem. But take an air sample or put a new clean filter, and that will not be the case. To be honest, I think there is too much paranoia / borderline OCD on TBN regarding hydraulic fluid changes. People seem to carry over logic from engine oil, and that does not apply to hydraulic fluid in any way.
A couple years ago, someone posted pictures of massive amounts of metal shavings (yes, actual shavings) caught in their HST filter. Now *that* was a problem and cause for concern, and clearly abnormal. Night and day from what we're looking at here. In that case, not only was a fluid change called for, but Kubota got involved as well.