"not true to seed" takes a little bit of explaining. Unlike many other common citrus varieties, Meyer produces all zygotic seeds, meaning they all resulted from sexual reproduction. Whenever this happens, the genes get mixed around. It will not be genetically identical to its parent. That being said, for some types of citrus, especially sour types, even if it is not a genetic clone it will likely still have fruit extremely similar to its parent (assuming the seed did not result from pollination with a different variety). Meyer lemons grown from seed are usually not as good, there's a 50% chance it will not be as sweet, and a 50% it will be insipid. Furthermore, when you grow from seed and the little tree has never been grafted onto different rootstock, it will take a very long time before the tree ever begins producing fruit, and the tree will be quite big at that time. (You see the dwarfing effect of rootstock induces a tree to begin producing fruit earlier in its lifespan, this is true with many fruit species, not just citrus)
Usually, for the home grower, it's not worth the effort, risk, and time growing from seed. But it can be done. And sometimes (in rare cases) you get a new variety that's better than the original.