Is this kind of situation possible?

usually when I see an SPI >1, I perceive this as project is ahead of schedule.

However, while reading PMBOK p. 183, I noticed that "...SPI measures all project work, the performance on critical path must also be analyzed to determined whether project will finish ahead of or behind..."

I can now think of the case when team has very good performance on non-critical path activities which is making SPI > 1, while SPI specifically for critical path is < 1 which is probably going to delay the project.