It seems to depend on where you look. I also have a $50K HELOC.
Presently I can only access my reports via CreditKarma (TU & EQ) and my EX report on Experian's site, without paying. On CK my HELOC is listed as a real estate loan, but on EX it shows up under revolving credit, and appears to count toward utilization, though maybe not for the actual FICO score (my score fluctuates depending on CC utilization, which the HELOC would buffer if it was considered part of this). But in EX's summary, it's not listed under credit cards or under real estate, only under open accounts. The My Debt Summary section shows my HELOC balance under "Credit and Retail Card Debt".
I'm also in the opposite situation of yours... I am refinancing to pay off my ex so I'm going to be losing my HELOC in a couple weeks, and going back to a conventional mortgage We'll see what happens to my scores when that happens. Sigh.
So EX seems to treat it as revolving credit, at least on the consumer website. TU and EQ may see things differently.
I think I've read that credit lines of $50K and higher aren't counted toward utilization for scoring, so that could explain the anomalies on my EX score vs. utilization shown on the website.
I don't recall what my score hit was when opening the line back in 2017, though my scores were lower then than they are now. I can only venture a guess as to what will happen after my refinance closes, the new mortgage reports and the HELOC is closed. I'm sure I'll see a score drop for a while. I'm debating whether to slip in a new credit card app between the time I close and the time the changes report.
New accounts, closed accounts tend to cause score drops for a period of time, but then letting things sit and age (gardening) lets them go back up over time.
Thanks for the details of your situation and how the three CRAs treat the line.
I don't think the CRAs are treating the line differently, just that DaB is seeing different CMS software display it differently.
DaB, have you pulled a copy of your real credit report? Remember what matters is what your real credit report(s) state, as those are what a potential lender pulling your report would see. They of course don't see any fluff or online reports provided by places like Experian or Credit Karma, so if their software displays an account incorrectly in the grand scheme of things it isn't a big deal.