Boccob has a +127* bonus to Spellcraft. Skill checks are handled by rolling a d20, and adding the bonus. Intermediate+ gods have a special rule that overrides the general rule, and count as having rolled a 20. So Boccob always gets a 147 on Spellcraft checks.
There are rules for calculating the DC to recognize a spell. Determining whether Boccob recognizes a spell or not followes game physics by following those rules.
If the GM decides that they want recognizing this particular spell to be a tense game moment, and replaces those rules with a coin flip, then they have ignored game physics.
* Although, from his stats, I don't see how, so this itself may be a typo, or may break game physics.
I really need to come up with better words to explain this idea. "Where do babies come from? When a Mommy and a Daddy love each other very much..."
Where does railroading come from? It comes from the existence of rails. Where do rails come from? They come from the GM wanting something.
Where does photosynthesis come from? It comes from plants processing sunlight.
So photosynthesis is sunlight? So photosynthesis is the sun? No. But understanding the sun's role in the process is part of understanding photosynthesis. Understanding the role of the GM wanting something (and not getting explicit buy-in) is part of understanding the nature of railroading.
Wrong. Photosynthesis occurs whether anyone notices or not, a murder is still a murder whether or not anyone complains, whether or not the murderer gets away with it. Railroading is equally defined by what it is, not by perception.