Similes use words like "like" or "as" to directly compare two things, while Greg's descriptions are more figurative and don't follow the strict format of a simile.
For example, Greg might describe something as "weird" or "totally embarrassing," but he doesn't say it's "like" something else. He uses his own, sometimes quirky, language to paint a picture in the reader's mind.
However, there are instances where Greg's descriptions *could* be interpreted as similes by a reader. For example, he might say something is "as boring as watching paint dry." While this doesn't use the exact structure of a simile, it functions similarly by comparing boredom to a specific action.
Ultimately, whether you consider Greg's descriptions to be similes depends on your interpretation.