Schroeder’s both old and young universe model does work as far as the science is concerned. From the point of view of an observer travelling at almost the speed of light, the age of the universe could be six microseconds or six thousand years or any other value less than the age that would be measured by an observer at rest relative to a specific part of the universe, depending on the exact speed. For example, to get the earth to age only 6,000 years to you when an observer on earth would see 4.56 billion years go by, simply travel at 0.99999999999913434903047053945162 times the speed of light.
Exegetically, it is somewhat problematical to explain why Genesis 1 would be written from the point of view of traveling at close to the speed of light.
Note, however, that this model contradicts standard young-earth teaching. Usually it is claimed that science “properly understood from a young-earth perspective” indicates a young age for the earth, whereas Schroeder affirms that science indicates an ancient earth if you are looking from the viewpoint of someone on earth.
Schroeder has endorsed some incorrect claims about other aspects of creation though, such as repeating the lie that Cambrian fossils were hidden away because they posed a challenge to evolution. In reality, the Burgess Shale fossils were reported in numerous scientific publications and even National Geographic in the early 1900’s. The claim that these fossils are a problem for evolution is based on interpretations of their identity that began to be developed in the 1970’s as they were restudied with new techniques and based on improved dating in the 1990’s of the relevant layers that decreased the time involved for the Cambrian “Explosion”. No, Walcott did not hide the specimens in museum drawers because of claims about evolution that would be made decades later. And specimens were distributed to numerous museums. I actually have a fossil from the Burgess as a result of that.
The basic problem with faith being strengthened by young-earth teaching is what that faith is in. The more someone hears that young-earth claims are the best explanation for everything, the more they may trust in those claims. But that is not faith in Christ; it is faith in the traditions of creation science. The testimonies promoted in the YEC community tend to be “I used to be an evolutionist but now I’m a creationist”. But a Christian testimony is “I am repenting from my sin and trusting in the saving work of Jesus.” Creation science distracts from Christ.
It is also quite problematic that “science properly understood from a young earth perspective” is an incoherent mix of claims. There is not agreement within YEC about what that science looks like. Even within one individual’s claims, often there are contradictions. If someone is serious about promoting YEC, they need to pay attention to the quality of the arguments, rather than relying on quantity. There can be a range of views within a movement, but admitting to that range rather than claiming that my idea is the one and only YEC view is important for honesty and clarity.