No, it isn't. The human body developed to bounce in and out of ketosis all the time. It's only hard to enter if you are always in a fed state and rarely in a fasted state. When you're fasting, it's not particularly hard to get back into ketosis in the same day, although it can take 24 to 48 hours for someone who isn't getting even light exercise. That's still way, way faster than the weeks it can take to get into ketosis on keto. (unless maybe you want to eat mostly protein and little fat, which is miserable)
I speak from extensive experience. A few weeks ago, after a 72 hour fast, I chowed on a pile of salmon sushi, measured my ketones throughout the day with ketone test strips, and was back in dark purple by the end of the night. Though normally it takes until the next morning for ketones to start showing up in my urine again, I believe it happened much faster because I was walking a lot that day. That was impossible to do back when I was just eating strict keto macros.
Anyone who doesn't believe me should try themselves by doing a few 72 hour fasts and refeeding on high protein, moderate carbs. They'd be surprised that it doesn't take an unreasonable amount of time to get back into ketosis. It's a perspective changer because it shows that occasionally eating carbs socially isn't the end of the world, because you'll be back in fat burning mode within a day or so.