They are "functional" in the sense that they are robust and capable of cutting objects, but they are not built in the same way that a functioning medieval sword would be. First of all, they are made out of steel instead of iron, which means that they are going to be much harder than modern swords. Secondly, they are not sharpened on one side only like most modern swords are. Instead, they have a flat surface called a "ground plate" where all the sharp edges are filed down. This makes them less dangerous to handle and more suitable for use as farm equipment. Even though they are not functional weapons, people still used them for entertainment and practice long after they were invented. They were popular among military personnel who needed something to fight with while waiting for their real weapons to be repaired or manufactured. Also, since they are very easy to find parts for (just by searching online you can order ground plates and scabbards in almost any size you need), it is no surprise that some makers decided to upgrade their designs by adding metal working tools such as saws and grindstones to them. These "play-weapons" are quite rare now because they are used for training purposes rather than for fights, but they are still found in museum collections around the world.