unless you think it is the exchange itself making the orders and increasing the volume, the Wash Trading is real trading. there are real people buying real coins with real money and paying real fees for each trade.
i think in the end the real question is: does it matter?
in stocks market or even in altcoin market where there are different choices you may look at the volume as an indicator. for instance you may go to a stock that has a higher volume that day. but when it comes to Bitcoin, people don't choose it because it had high volume!
among bitcoin exchanges like the Chinese ones which were reporting ridiculously high volumes it was done for competition so that you choose exchange 1 over exchange 2.
coinmarketcap says trading volume was $4.5 billion. lets say half of it is Wash Trading volume! do you think it would matter if volume was $2.25 billion? you think people would stop investing in bitcoin just because the volume is lower and would invest a lot more because the volume is higher? i don't think so.
The conclusion is ultimately wrong. Trading volume is a significant data point when considering price movements. Higher volume gives the appearance of more consensus and legitimacy that the price is sustainable. That's why wash trading is potentially an important issue, because if some of the data is faked or isn't reliable, it undermines confidence in the systems.
If a stock goes up in value from $5 to $10 dollars in a single day, that's a huge gain; 100%. If the average daily trading volume is 100,000 shares and it goes up 100% on a trade volume of 25,000 shares, this is a potentially important data point telling us the price is not widely accepted by the market to be indicative of true value. It could be one trader who is out of his mind or will ultimately be proven to have greatly overpaid for his shares. However, if the price goes up 100% on daily trading volume of 500,000 shares, we now have a 5x increase in average trading volume, which tells us that the number of people who are consensus over the new valuation is significantly higher and the price increase is more likely to hold. In investing, market consensus is pretty important, since the wisdom of the crowd often prevails and the odds that everyone is wrong diminishes compared to one guy.
This is why trading volumes matter. The fraudulent trading volumes by the Chinese exchanges are meant to give the appearance of more consensus and to trick investors into trading more so they can earn more in fees. They are obscuring the risks of investing by hiding what may be far more shallow markets that would keep risk-averse investors away. It is not defensible in any way, and not a small deal.