1. ALL the staves are WAY too far apart. For this style of writing, the staves should be closer together than usual.
2. Beaming to the beat would be much more legible, no matter what style of beaming is used.
3.I don't think that the situation is exactly like that of a percussion score, which is best left to the players to divide up.
If it is educational music and/or this was written by a virtuoso mallet player, I think that it is appropriate for the hand divisions to be specified in the notation itself, just as keyboard composers generally specify such decisions. In music written by an composer who is an expert on the instrument, the music and the way of playing it originated at the same time. So the composer has already found the best way to accomplish the passage technically, and the passage is best expressed with the composer's division.
But if this is NOT the case, which is probably the most common case encountered by percussionists, the music should be left without hand divisions.
While it is clear that the engraver was inexperienced and making a lot of errors while using old Finale defaults etc. I do agree with his notation here. The first B-E leads downward; the second B-E leads upward and the split between the staves makes a nice transition.6. EX1 m.1: why is tone B-E in LH in ? But the next B-E in m.3 in is split in ? What is the sense of it?