Just because they currently act more against chat offenses does not mean that they are prioritizing those over other offenses, it is just that those offenses are much easier to catch and therefore are punished more quickly than other forms of trolling.
The reason they catch text chat offenses so much more often are not because of priorities, but because of effectiveness of systems. It is a comparatively trivial task to parse chat and punish people who misuse it, while the act of detecting, verifying and then double and triple verifying to avoid false positives with gameplay trolling is much much harder and more time consuming.
It's not that they are prioritizing chat over trolling, it's just that they are punishing what they can with what they can do right now, which happens to be overwhelmingly high number of chat offenses compared to gameplay offenses. They actually are working on systems to better detect gameplay trolling rather than on more complex chat detection systems, so their priorities actually are 'straight' according to your argument.