Hmm, this seems a bit off.
Mate, maybe you told the OP the wrong target. Because the best opportunity of buying did not come on 9th May the dip that came on May 11th May means that the price had declined from its peak and reached straight-forward support. That is, the BTC price fell from 63,469 to 60,187 in only 4 hours. Which refutes the statement of the best time for investment. 
 
Apart from this, you may not know that according to technical analysis, Bitcoin was moving in a symmetric triangle within a 4-hour time frame. where the decline line was $63,000 and the support level was 60,000. And you see, this is what happened, that is, the price rejected the same at 63k and 60k provided the best opportunity for investment, which is also called a small dip, so it will not be bad. 
 
So, all these mentioned posts of mine will give a good awareness that the market did not give a better opportunity for investment on 9th May but on 11th May.