Basically the entire reason for kosher laws is to force “advisable” behaviors on people. Pork is banned because it can cause trichinosis. Shellfish are banned because they can have red tide poisoning. The knowledge was far less, so many of the laws don’t actually make sense, but basically it was the educated leaders making decisions about how people should behave and then creating religious rules to ensure compliance.

In this way, yes, the ban against texting is cherry picked, but only as much as everything else. The rabbis have basically decided that texting is bad, but being available for calls is good (a not unreasonable opinion), so they’ve called it “kosher” to invoke the authority of G-d to support their decision.