I would not say "easily"... patent holders will absolutely try to avoid the effects of exhaustion by imposing post-sale or field-of-use restrictions, but lawsui

I would not say "easily"... patent holders will absolutely try to avoid the effects of exhaustion by imposing post-sale or field-of-use restrictions, but lawsuits about it have gone to the Supreme Court, e.g., https://supreme.justia.com/cases/federal/us/553/617/ https://supreme.justia.com/cases/federal/us/553/617/ (and not worked out well for the patent holder).