While Japanese schools are indeed required to teach English, they mostly do simple vocabulary up to 3rd/4th grade in elementary school and only get to simple sentence structures (without teaching them grammar) in 5th/6th grade, and a bit of an introduction to the alphabet. That said, a good portion of them take English lessons outside of school at this stage. Starting in middle school, they finally touch on phonics, and begin to put the sounds to the letters, which they are formally taught simultaneously. From here things speed up a bit and the kids are introduced to English grammar which is very different to Japanese grammar.
I'm not sure how long ago Gaijin Goomba was teaching English in Japan, but it must've been quite a while ago. The situation you described above is no longer the case. So yes, while you might be shaking your head at this curriculum and pace, the teachers themselves, especially at the elementary level, are not equipped to be teaching English at a higher level than just simple vocabulary and sentence structures.