If 50% of the stocks in two funds are the same, then investors should observe whether there is a big difference in the holdings of these 50% stocks. For example, if the top ten stocks held by the two funds are the same

Yes, then there is no need to buy the two funds together at this time.

Because the funds are counted as duplicates.

If two funds buy 50% of the same shares, but the top ten positions are not the same, then it is not considered a duplication, and the two funds can buy them together.