Piano score with LH notes in RH staff using a long stem

Frequently a piano score has notes written in both staffs for the same hand. This avoids having lots of ledger lines that are hard to read. In the 2-measure example attached, the left hand plays eighth-note triplets starting in the bass clef, where the last note of the triplet is written in the treble clef staff right along with the right-hand notes.

Using a second voice in the upper staff isn't the same, because it doesn't show clearly that the note is to be played by the left hand. In the example, the triplet bar connects all three notes, and a long stem extends all the way up to the third note of the triplet in the treble staff.

This is not uncommon, and might deserve some development time.