bug: emoji grid rendering inconsistency

[tauraamui]

So on an emulator such as wezterm, regardless of the font size/or zoom level, this test TUI program I am using (to help improve emoji support for lilly) which renders a grid of emojis of cell width 2 consistently renders as a grid for the full available window/pane size. The below screenshot shows the output as I expect it.

This following gif demonstrates what I am seeing when I zoom in and out using the same program within Rio. I am unsure what is actually happening within Rio to cause this behaviour, but I imagine it's something to do with fractional calculations of cells and what they can fit?

output.mp4