The Wall Street Journal has misunderstood the situation and the proposal [emphasis added].

President Donald Trump’s executive order on health insurance, the most significant step so far to put his stamp on health policy, is designed to give more options to healthy consumers. It also could divide the insurance market in two.

What Trump is purportedly going to do with his Executive Order is

• instruct[] federal agencies to loosen rules on health plans that the administration says have driven up premiums and reduced insurance offerings
• direct the Health and Human Services, Labor, and Treasury Departments to lay the groundwork for the growth of association health plans, coverage that would have fewer mandated benefits than many current plans available to small employers and individuals [and] that wouldn’t be subject to the full range of ACA requirements, such as the mandated package of benefits.
• departments, in addition, will be told to take steps to expand the availability of short-term medical plans …  allow people to once again buy plans in that category that could last for almost a year.

However, rather than create two health insurance markets, these actions would do no more than begin to create one health insurance market.  There is no extant health insurance market; there is nothing present to become part of “two markets.”  What we have presently is neither insurance nor a market for it.  What we have is a health coverage welfare program that has some (very poor) options from which we’re required to select one for ourselves.

The beginnings of a health insurance market, in addition to being an actual market for health insurance, would, though, lessen the importance of the mandated welfare program—to the benefit of all of us, including those trapped in that welfare program.