The computer industry is notoriously unstable with jobs often quite short term in practice, with layoffs common.
Just to be clear, the referenced AIP report starts with the phrase:
Positions accepted by PhD degree recipients following receipt of their
degrees fall into three categories: postdoctoral fellowships, potentially
permanent positions and other temporary positions.
The figure on page two of the AIP report specifically lists a "private sector" block under "potentially permanent".
Tabel 1 on page 3 lists 70 percent of potentially permanent positions as "private sector." Again this is very misleading as private sector positions are potentially permanent only is the sense that there is a small chance that you might continue at the same employer until retirement; there is nothing like a guarantee.
To me "potentially permanent" seems like a serviceable phrase to encompass positions in academia and in industry that do not have an end data built in to them. It contrasts them to "temporary" positions like postdocs in academia or contractors in industry where you know going into the job that your employment ends on a certain date.
The primary audience for a report on outcomes for Ph.D.'s in Physics one year after graduation, getting their Ph.D. degree, is students (and parents of students) evaluating whether to pursue a Ph.D.. Obviously, they should investigate longer term outcomes, but young people often don't, focusing the next step in their life/career.
Potentially permanent position sounds like a general version of "tenure track research job" as another commenter correctly noted below.
Students with little or no work experience often do not have an accurate impression of salaries, working conditions, and other aspects of the work world (or academia), specifically in the private sector computer industry where most Ph.D's in Physics currently end up.
News coverage of computer companies like Google emphasizes many far out research-like projects such as the Google self-driving car, the AlphaGo deep learning project, and so forth. These sounds like academic research, so why wouldn't these companies have comparable positions to tenure track research jobs? Indeed, in very rare cases, they may have such positions.
However, the vast majority of industry jobs are at will full time jobs without a specified end date. Especially in the computer industry, they are quite insecure and often short-lived, very different from what potentially permanent position implies. They are not analogous to tenure track jobs.
My job is described as permanent full time, because my contract is ongoing, and I work 40 hours a week; when I was a student, I had a permanent part time job.
This is in contrast to a casual job, which in New Zealand is similar to at-will (but with strong restrictions on what roles can be casual); or a fixed term contract.
In any case, with the closure or heavy cutbacks at corporate research labs, AIP should update its language to reflect current realities.