This is because they are incompatible with C++ and possibly other
languages that make them minimum size 1 (to make sure multiple
such objects don't reside at the same address). Forcing them to size
1 was also not practical, as that is requires updating the logic
of a lot of implementations and thus possibly backwards incompatible.

More here: https://github.com/google/flatbuffers/issues/4122

Change-Id: I2bfdc8597b7cfd2235bb4074bb2ae06f81f8e57d