Even though Synchro Monsters typically do not have the text “Must first be Synchro Summoned”, they are nonetheless all treated as Semi-Nomi  monsters, i.e. they cannot be Special Summoned from the Graveyard or banished zone unless they are successfully Synchro Summoned first. The same goes for all other extra-deck monster cards - Fusion Monsters and Xyz Monsters. This often leads to confusion if such a monster is Special Summoned from the Extra Deck by any other means. The most notorious example of this is “Starlight Road”:



Since “Starlight Road” does not include the text “(This is treated as a Synchro Summon)”, “Stardust Dragon” is treated to have been brought to the field without being Synchro Summoned first. This means that if you activate its effect, it will go to the Graveyard without the ability to be Special Summoned back from it, even by its own effect. Hence the ruling that a “Stardust Dragon” Special Summoned by “Starlight Road” will not Special Summon itself after negating a destruction effect.

This ruling is a reminder that you should never rely on common sense alone when playing a competitive game. Every phrase on a card has a formal meaning, and “leaves the field” is no exception. According to the official rules, “A card leaves the field, formerly known as being removed from the field, when it is returned from the field to the hand or Extra Deck, sent from the field to the Graveyard, or banished from the field.” Note that that does not include “Is attached or detached”, meaning that, formally, when a monster is attached to an Xyz Monster as Xyz Material, it ceases being on the field without actually “leaving” the field. This is important because it means that effects that trigger on “leaving the field” will never activate:



At the same token, when a monster is detached, it is not considered to be on the field prior to that, meaning that “When this card is sent from the field to the Graveyard” effects will not trigger either:



However, effects that do not care where they were sent to the Graveyard from, will activate:

Always read your cards’ text carefully. Because sometimes just a few words can dramatically change what you can and cannot do with it. The “When..: You can…” pattern is exactly that, because it means that the card’s effect can “miss timing”. What does that all mean? Consider the three following effects:

“When a monster on the field is destroyed: Draw 1 card.”
“When a monster on the field is destroyed: You can Draw 1 card.”
“If a monster on the field is destroyed: You can Draw 1 card.”

On the surface they all look the same, and it would be reasonable for you to expect that they all work exactly the same. But they don’t. Because of its wording, the second effect will miss timing if “a monster being destroyed” isn’t the very last thing to occur. This can occur if, for example, the effect that destroys the monster is Chain Link 2 or higher, meaning some other effect still need to resolve afterwards. Other times this is caused by the event triggering the effect being only the first of a series of actions that comprise an effect, such as in the case of “Ryko, Lightsworn Hunter”:



This means that you cannot hit the “When” part on that effect – the opportunity is missed. However, in the same circumstance, the other two effects will not miss timing. Why?
The first effect will trigger because it does not include a “You can” after the colon. This means that the effect is mandatory – you cannot choose not to activate it, therefore it must trigger, even if not at the exact same time as its condition was met.
The third effect will let you choose whether to activate the effect after the chain has finished resolving, because “If” does not imply a specific timing the same way “When” does. Therefore such an effect cannot “miss timing” – there is no timing involved at all.

So, long story short: watch out for “When..: You can…” effects. They are easy to miss, but they behave differently to other effects, and can sometimes cost you the game.