If we are going to use the word "Default" as a purpose of summoning monsters through an effect, then I would think that by "Default", a monster cannot be summoned from the Fusion Deck unless the effect states that you can Special Summon a Fusion Monster "somewhere" in the text of the effect.
Clearly
Machine Duplication does not state that you may Special Summon Machine Fusions, and it's not like this card is from a early set (Rise of Destiny), so I dont see how hard it would have been to put a few more words on the card's text to state
"Select 1 Machine-Type monster with an ATK of 500 or less on your side of the field and activate this card. You can Special Summon up to 2 cards with the same name from your Deck
or Fusion Deck."
Three little words.
I cant see where this card can do what
Mystic Tomato,
Mother Grizzly,
Flying Kamakiri #1, and
Giant Rat can't.
Mystic Tomato
Card Text
When this card is sent to the Graveyard as a result of battle, you can Special Summon 1 DARK monster with an ATK of 1500 or less in face-up Attack Position from your Deck
or Fusion Deck. Then shuffle your Deck.
Mother Grizzly
Card Text
When this card is sent to the Graveyard as a result of battle, you can Special Summon 1 WATER monster with an ATK of 1500 or less in face-up Attack Position from your Deck
or Fusion Deck. Then shuffle your Deck.
Flying Kamakiri #1
Card Text
When this card is sent to the Graveyard as a result of battle, you can Special Summon 1 WIND monster with an ATK of 1500 or less in face-up Attack Position from your Deck
or Fusion Deck. Then shuffle your Deck.
Giant Rat
Card Text
When this card is sent to the Graveyard as a result of battle, you can Special Summon 1 EARTH monster with an ATK of 1500 or less in face-up Attack Position from your Deck
or Fusion Deck. Then shuffle your Deck.
Three little words can change everything we know about the game to date.
Maybe in the future they will make a
"Fusion Duplication" Card, and it will have basically the same type of effect as
Machine Duplication, and it will be Banned or restricted/limited as quicky as it is made.