seeds will grow to carrots if replaced by villagers

Villagers plant random crops, not only the kind just harvested.

No, villagers will place crops they just harvested, and if they harvested carrots, they might plant carrots instead.

Well, yes. You are right.

But - is the described issue a bug ?

User plants seeds, villagers replace the seeds by carrots.

Well, he needs to give more detail, in the screenshots he is in a village with carrots around, if the villagers had farmed the carrots first, they will replace the other crops with carrots they just harvested, so it's possible this was the case, has happened to me all the time. Over time it's like the village has only one dominant crop from so much harvesting and replanting. This isn't a bug, they just replant what's first in their inventory. Also if you look in the first and last screenshots, the wheat and carrot seedlings have different textures, so they did plant down carrots. It even looks like the carrots were already harvested beforehand.