For Federal Pell Grants, Is "Half-Time Enrollment" the Same As "50% Enrollment Intensity?"

Yes. According to U.S. Department of Education's (ED's) FAFSA Simplification Questions and Answers, PEL-Q4/A4:

"PEL-Q4: The regulations in 34 CFR part 690 refer in places to “half-time enrollment.” How do we account for this with enrollment intensity?

PEL-A4: We consider any regulatory reference to “half-time enrollment” status to mean 50% enrollment intensity. For example, under § 690.6(c)(4), an otherwise eligible student who has a baccalaureate degree and is enrolled in a postbaccalaureate program is eligible to receive a Pell Grant for the period of time necessary to complete the program if the student is enrolled as at least a half-time student. Following the implementation of the changes relating to enrollment intensity, this provision would apply to any student enrolled with 50% enrollment intensity."