You present an interesting point. The answer is yes, the rotation is controllable and I know which pages have been crawled. But it gets even more complicated. Attorney’s listings/content are dynamically swapped out/in depending on the location of the visitor (no reason to show a Dallas attorney to an Austin visitor or a Califiornia attorney to a Texas resident [unless they expressly ask for that]). So to make sure all pages get indexed we have to ensure that Googlebots (which are all coming from an irrelevant location), as well as others, see all the pages. And herein lies one of the reasons I was looking for outside confirmation of the backlinking, to validate what I think I already know.
Another factor is that some listings are free/trial and have a particular expiration, they get slowly rolled out of rotation unless they opt-in. The free trial is an important marketing tool. Before their time expires we want to be able to tell them ‘Hey, you got x number of views, x number of click-thrus, and x number of bot-crawls/backlinks’.
Another reason to track outbound backlinking is that in addition to branding (impressions) and click thrus (case potential/traffic), there is also some perceived value by the attorney (real or not) to these links. Many attorneys, precisely BECAUSE of the recent emphasis by Google targeting link farms and other schemes, see value in getting authoritative backlinks from a legal reference site that has been in Google’s index for 15+ years.
We don’t charge for these links, they are simply a byproduct of the listings. Each listing contains value added content (annotations) related to the law in view. Because the listing is actual content (not just a name and address) and because it links to another authoritative legally related site (the attorney’s website) this is very Google friendly. The value added content contains anchor text (in context) with keywords related to the law being viewed as well as keywords on the targeted page of the attorney’s website.
So, the end user gets layman language about the law they are reading, and the attorney gets a funnel from a potential client with a specific problem to his/her website. Both parties get link association with original content (not a simple link list) containing carefully crafted anchor text. Our research has shown that attorneys and their SEO/IT personnel see value not only in branding, and click-thrus, but also the backlinks. Actually, I had overlooked the backlink angle altogether until recently when I was approached by an SEO professional representing several law firms. What got his attention was the backlinks that appeared in his own reports. This was cool. I didn’t have to find him, he found me. 
Each listing can end up on thousands of pages of law and search results. They see this as just one more reason for opting in. Really, it’s a good trade, they often get hundreds of back-links where we may only get one (or none) from them.
There may also be some small value in indirect acceleration of bot crawls on the target websites because of the large number of pages containing the target link. Our sites are crawled continually 24x7 by all the big bots.
It’s all still somewhat experimental at this point. I’ve been publishing the law as a free public service for 15+ years. When I began, the primary audience was the Texas Judiciary. But over time, with the rapid expansion of the Internet at large, the resource is now used mostly by non-lawyers with legal problems. And so we have been developing ways to use the resource to connect attorneys with clients beyond just a simple ‘legal directory’ or advertisements (which no-one pays attention to anyway).
At this point I’m pretty sure AHREF is using their own crawlers and the info there is NOT coming from Google.
If you got all the way through all this, hats off to you…
Sorry for the rant. Hope it helps you understand where I’m coming from. Thanks for your patience.