There is an important difference between a mature creation and apparent age. God is not deceptive and would not create things with a false appearance of age. But he did create things mature. Careful study can show the difference.
For example, while Adam was created as an adult, and adults usually have to go through the childhood stages to reach adulthood, Adam didn't. He was created mature. However, he was not created with false signs of aging. Thus, on first glance, a doctor examining him right after his creation would think he was 20 or 30 years old due to the body size, ability to grow a beard, sexual maturity, etc. But on closer inspection, the doctor would notice something peculiar. There would be no wrinkles, no scars, no callouses, no belly button. Adam wouldn't show signs of actual aging or having lived years on the earth or having been injured in events that never happened or having been born. If he had, that would be apparent age, not merely a mature creation. Close inspection would be needed to indicate the difference. Whereas a cursory inspection and initial conclusion might point to a man who had lived a couple decades or more, closer and more detailed inspection would give reason to think he hadn't actually started as a baby and grown to adulthood, and thus the appearance of age would disappear.
Much the same thing is true when we study our planet as well. On first glance, there are a number of features that look, superficially, to be signs of great age. On closer inspection, there is evidence that they did not actually take a long time to develop.
One might look at the amount of sedimentary rock on the planet, which would indicate millions of years of slow sediment deposition (which is the way we usually get such sediment deposition), and think the earth is millions of years old. But on closer inspection, we see that there is little or no erosion between most of those layers and there are animal and plant remains in the layers that appear to have been buried very rapidly and are well preserved and in positions that indicate catastrophe. There are fossils that extend between more than one layer. There are soft tissues found in some of these fossils, including in the remains of dinosaurs, in which individual cells and their parts can be distinguished quite clearly. These features and others lead one to believe that the sediment did not actually take millions of years to deposit and that another, more rapid and catastrophic explanation fits the evidence best.
Perhaps the most problematic use of apparent age is to explain away distant starlight by suggesting that it might have been created in transit rather than originating at the actual star. Yet this would be apparent age, not merely a mature creation. Mature creation is creating an actual star instead of a dust cloud that must condense into a star. Saying that the starlight we see that appears to tell us chemical composition, location, distance, motion, and also events that have happened to that star (such as exploding into a supernova) did not actually come from an actual star or actual events would mean that starlight serves only to deceive through apparent age. What's more, if that were true, then the night sky is all a sparkling facade - a light show with no substance - and we have no ability to know what is actually out there in space or to study it. There are several potential explanations for distant starlight reaching a young earth, but apparent age is not one of them.
The fact that God created Adam as a grown man and trees that never grew from seeds and animals that were never juveniles does not allow us to ignore evidence of age like celestial events or to fail to seek good explanations for things like rock strata that might look superficially old. We can't lump all those things together as if they were all the same kind of thing. That's lazy and ignorant thinking. It's important to distinguish between apparent age and a creation that was simply created mature. We should not attribute deception to God or offer simplistic explanations that fail to account for the facts. Neither of those bring glory to God.