I think there's no harm in waiting for a slight decline to make purchases on bitcoin.
There is no harm as long as you have already bought some and even if you have been buying bitcoin regularly, persistently, consistently and perhaps even aggressively. If you have not already bought some bitcoin, then there likely is quite a bit of harm in waiting, since waiting is not a good mindset or practice, especially when it comes to bitcoin investing. So, yeah, I would suggest that there can be quite a few situations in which waiting, especially when it comes to bitcoin, is actually harmful even if the person might not realize the level of harm actually being done...
You are right, waiting for the price to fall to buy bitcoin is less relevant for novice investors who are just starting to invest. Because when beginners to bitcoin wait to make purchases, I think they will lose good momentum. So for beginners, it is recommended to make purchases where the cold money is ready. Then regarding the dangers of waiting to buy bitcoin, what you mean by my assumption might have a very complex meaning (especially for beginners). Because the worst thing that could happen when novice investors wait too long to invest in Bitcoin is that the money they were going to invest is used up by other needs. This assumption will certainly have some pros and cons, because it could be answered that it means the person does not have reserve funds or emergency funds. This could indeed be true. But in certain situations, sometimes even investors who have emergency funds cannot cover sudden needs.
Then secondly, waiting too long when buying bitcoin might have a quite negative impact on the way we view bitcoin. Because it could be that beginners wait too long for the price of Bitcoin to fall, and the price doesn't go down. This will change beginners' assumptions about Bitcoin. So it could be that the beginner gives up because he thinks the price of bitcoin will never fall again as he expected. Maybe the opinion I express is a little wild, but I have heard this from several people around me. Because it cannot be denied that many people now know about Bitcoin, but are hesitant to buy it because of its high price.