This has always been a trend and we should all learn from it.
Whenever you hear the rumour of any hardfork, you should know that it is meant to pump the coin that is to be forked. So, if you want to partake in it, buy it while the price is still low at the time of the rumour and do not hesitate to sell when it pumps, else whales most especially will dump on you.
Avoid being carried away by the news of hardfork.
It is a trend and that will always happen to every forked coin.
Just my candid advise!!!
That is the most common scenario for a hardfork, just like what you said the pump will happen before the hardfork.
To be able to safe with that condition, we should always keeping an eye on the market, so that we will know when will the dump might happen.