I agree with you, for someone to say that Bitcoin we keep increasing and not decrease is a very wrong statement to me, which can also be misleading, because if bitcoin keep increasing we will only have the bull run season which is inappropriate.
He is not wrong, he is right. You don't understand the term "increase in value overtime". It means that the more time passes by, bitcoin price will continue to increase in value which is true. Check out bitcoin history from 2009 till date, the price has been increasing. Bitcoin is still young and the price has the highest odd to increase overtime. Even if bitcoin dips, doesn't mean that it will crash to zero. But if it dips and after some period of time, it increases and makes a new ATH. It means that bitcoin price is increasing overtime. Bitcoin price will dip for it to be able to go farther above the initial high price.
for bitcoin to get good balance and still maintain it store of value there have to be both the bull season and the bear season, because of it Volatility, bitcoin increasing without decrease we make bitcoin no longer have store of value.
You don't understand the meaning of when they say an asset is a store of value and is not because that asset price goes up and down. Is land properties and real estate not a store of value. Do their price go down and pump like bitcoin, NO. Because land properties are not volatile asset.
The meaning of store of value is an asset that will not depreciate in value due to inflation but will always keep its value no matter how high inflation level is for example gold. That asset can also appreciate in value overtime.