Isn't this a marker of both gullibility and unscrupulousness? Would the author be okay with his current employees taking similar screenshots out of CRM and sharing those screenshots with other prospective employers?
If you ask this as part of a job interview process, you're signalling to the applicants that (i) you don't trust the answers they're giving you (ii) you don't trust your own ability to assess whether their communication is commensurate with their resume boasts (iii) you expect them to breach their employer's trust by sharing confidential sales figures in order to get the job.
If you're giving those signals in the interview, good salespeople will run a mile.
Average salespeople might still know their CRM system well enough to be able to run the statistic that paints them in the best possible light. And even if they can't prove they topped the activity stats for the outbound East Coast FMCG team last month (whilst they were on a final warning for poor figures), there's always Photoshop.
Companies that take these kinds of reports seriously will usually use a second source to verify the information. My old employer always tried to interview 2 candidates from the same company and region so they can compare the rankings and data presented by the candidates. There was also an informal network of information sharing as everyone had worked for everyone else in the industry at some point and had contacts they could reach out to. Plus, prestigious recognitions, things like Chariman's/President's clubs for top reps, usually get listed in some publicly available form (ours was in our quarterly fluff magazine available on our website).
Now is it ethical? I've noticed that there's a recognized line in sales culture between information concerning a rep's personal performance and proprietary company information. Things like stack rankings (scrubbed of $ figures), activity stats, close ratios, etc are considered kosher by everyone as they don't reveal anything that could realistically damage the company. Things like a rep's list of contacts, anything with revenue figures, etc are frowned upon as they are considered unethical for a variety of reasons. It shows the candidate is willing to damage their employer and knowing that data puts the hiring company in a bad legal position.
Salespeople are judged on their performance and their performance is unique in that it can be quantified in hard numbers. Sales culture has a high level of tolerance for sharing of relevant information as it benefits everyone involved. Candidates get objective proof of their value to a potential employer and employers get objective information, making their hiring decision truly informed instead of a subjective crapshoot like you find in elsewhere.
Most companies do maintain sales performance for each candidate however and this is usually safe to ask for. It wont let you compare across the whole company but at least you can verify their actual numbers as the company tracks them.