I recently performed a restore from a backup of 1.12.2 for testing. Upon restoring to 18w50a, I found that I could no longer repair or restore broken items by combining them, including on a crafting table.
In addition, before performing this - I played the same game at 18w49a and the performance was better. This snapshots has a "largish" feel if I may be frank.
They added a new crafting station called 'Grindstone'. It has two functions; one to repair tools by combining them and one to 'disenchant' things. I did not look in to them removing the combining feature, but I would assume with this new crafting station that they did remove it.