Since the Colvin junks, with their euphroes, have been discussed lately, I have wondered why these have been used. After having looked around, my guess ( I stress: guess) is that the euphroes have been inherited from the junkrigs with very many batten panels.

On the photo down to the left, the mainsail has 21panels. The mainsail has a central sheet where the load from the sheet is spread to the upper and lower half of the battens via two multi-hole euphroes,

In contrast, the 7-panel mainsail of the Hong Kong junk, shown down to the right, appears to have a much simpler setup. The sheetlets seems to go through a single-hole euproe, probably with a sheaved block in the other end for the sheet. This is more similar to how we do it.

However, the mainsail of that junk seems to have an other interesting detail:
The boom and the four lower batten appear to be connected to a central sheet. The upper battens, on the other hand, appear to be controlled by port-stbd. sheets. That makes sense.
My armchair conclusion it therefore that  there is no need for the euphroes for sails with  only 6-7 panels.

Arne

PS: It could be that the junk to the right also is sheeted to a larger euphroe, but that this has been hauled all the way down to deck here, as they are sailing close to the wind.