When you click on a square where two clues overlap (eg the top left square might well be the first square for both 1A and 1D), the crossword often selects the D clue first, you then have to click again to get the A clue. This is a change of functionality from before when the A clue was always highlighted first. We do always give the A clues first, so it makes sense to be consistent.
Another idea from guardian/dotcom-rendering#12993: if a cell has across and down options and one is complete, selecting the cell should pick the incomplete entry
Another idea from user reports: if the cell you click happens to be the first letter of a word, this is the word that ought to be selected. This is apparently the way the frontend grid worked.