It's perfectly possible that the nests found inside the fossilized trees were made by bees 200 million years ago. The arguments used by the skeptics are not convincing.
First, it's true we have no fossil remains of actual bees that date to 200 million years ago, but maybe the reason for that is that bees could not be preserved as fossils at that time. Fossil bees have typically been preserved in fossilized tree resin, a sticky liquid produced by trees. However, trees with this type of resin were very rare 200 million years ago. Such trees became common much later. So the fact that we have no bee remains that are 200 million years old doesn't mean that bees did not exist at that time. Maybe bees existed, but since there were almost no trees producing the right kind of resin, the bees could not be preserved.
Second, while it's true that bees have a close mutual relationship with flowering plants today, it's quite possible that bees existed before flowering plants appeared on Earth. Those very early bees might have been feeding on non-flowering plants that preceded flowering plants during evolutionary history. The early bees could have fed on non- flowering plants such as ferns or pine trees. Later when flowering plants evolved, bees may have adapted to feeding on them! And this new relationship between bees and flowering plants may have remained stable ever since.
Third, even though the fossilized chambers lack spiral caps, there's chemical evidence that supports the theory that bees built the chambers. Modern bees protect their nest chambers against water by using a special waterproofing substance that has a distinctive chemical composition. When the fossilized chambers were chemically analyzed, it turned out that they contain the same kind of waterproofing material that's used by modern bees.