This is a good hypothesis, but it is far from obvious.
I remember, years ago, unwinding a portfolio of correlation trades. The trades consisted of bets on how assets would correlate, e.g. Apple might be expected to correlate with Microsoft more than with Société Générale, a French bank. We were under a time crunch to unwind the massive portfolio. Given the structure of the trades, unwinding them meant reversing their implied correlations. Thus, for one week, the market's largest names anti-correlated with reference to how a few traders had previously thought they should have correlated. The moves were noticeable; the attribution far from obvious. Nevertheless, talking heads proceeded to breathlessly blame political crises in Spain.
To properly attribute this Bitcoin activity to the People's Bank of China, one would want to examine country-level Bitcoin flows of funds around the time of the PBoC announcement, paying attention to hourly data around when the Chinese- and English-language announcements were made/leaked.