Put a hoe in the offhand slot and seeds in the main hand. You're unable to till grass blocks.

This is unexpected because the opposite works smoothly: put seeds in the offhand and hoe in the main hand --> you can till the block and then plant seeds.

It ought to work the other way around too. Essentially, the logic should be "if main hand item cannot be used, try the offhand item". Seeds cannot be used on grass blocks, so it should fall back to using the hoe - but it doesn't for some reason.

The reason this is important is because seeds don't automatically get put in the offhand slot when picking them up. Therefore it would be more convenient to hold the hoe in the offhand slot and pick up seeds in the hotbar, especially when farming a variety of different crops.