The Fletcher Villager does not appear to gift Arrow of Slow Falling or Arrow of the Turtle Master, despite being able to gift all of the other Tipped Arrow types, and despite selling all Tipped Arrow types as a Master level trade (with the exception of Arrow of Luck of course).

Place and activate a repeating command block with the command "loot give @a loot minecraft:gameplay/hero_of_the_village/fletcher_gift". You just won't get the two arrow types mentioned, despite them being available as villager trades.