Shemitah lechumrah

Answer

Shemitah lechumrah is a commercial buzz phrase, without halachic significance. The intention of the phrase is produce grown by non-Jews and Arabs inside and outside of Israel, and import. Those who eat heter mechirah are essentially eating the produce of non-Jews, so they can eat shemitah lechumrah produce. However, remember that buying shemitah lechumrah produce assists non Jewish farmers (Israeli Arabs and Palestinians), which presents the problem of strengthening them. It is best to buy otzar beit din produce and observe kedushat shevi'it.