So are their results, when compared against US News, for example.

But more on WSJ's questionable methodology (straight from the BYU-I web page, with my thoughts in italics): 

The Wall Street Journal’s rankings are decided primarily by average student outcomes, which include salary impact, years to pay off net price, and graduation rate impact.

• Salary impact measures how much a college boosts its graduates’ salaries beyond what they would be statistically expected to earn. 
  • There's a lot hiding in the phrase "beyond what they would be statistically expected to earn." To whom are we comparing these BYU-I students? High school grads in rural Idaho/Montana? Each applicant's high school cohort (regardless of where they went to high school)? Theoretically, this statistic could be gamed by founding a college in a remote, rural area and drawing applicants from more populous areas, especially if those applicants get a degree and then return to higher COL areas (with commensurately higher wages) for work. Oh wait, that sounds just like BYU-I...
• Years to pay off net price combines the average full cost of attending the college and the value added to graduates’ median salary by attending the college. 
  • Schools with very low tuition would do well in this metric, regardless of quality of education... A theoretical school with $10 tuition would dominate; regardless of quality of education, a graduate could pay off their tuition in one shift at McDonald's. One wonders whether BYU-I experiences a similar (but less dramatic) boost in WSJ's rankings due to the Mormon church's heavy tuition subsidies
• Graduation rate impact measures the amount of students who graduate from the college compared to the amount that would be statistically expected.
  • Not sure this is a feather in the cap of BYU-I. On the one hand, good for BYU-I for getting people graduated. On the other hand, if everyone graduates, is it that hard?