Question: What happens when two players call the same tile for Mah Jongg?

Answer: When two players call the same tile for Mah Jongg, the player next in turn gets the tile. However, there is an exception to this rule. If two players call the same tile for Mah Jongg, and one has exposed tiles, they are entitled to the tile regardless of whether they are next to pick. Exposed tiles in this case means, tiles that will be a part of the grouping with which the called tile will be used. As an example: Player B calls a 6 Bam and Player A calls the same tile, both for Mah Jongg.  Player B took the other 6 Bams from her rack and placed them on top of her rack, before Player A took action. Although Player B is not next in line, they get preference and would be entitled to the win.

Source: Mah Jongg Made Easy 2024 edition, pg. 18, #10(c)