An excerpt from IRS Notice 2018-95 - and short answer is that in your example, you can exclude them under the "20 hour" exclusion. Emphasis is mine.
The provision imposes three separate conditions for an employee to be excluded from making elective deferrals under the part-time exclusion: (1) a “first-year” exclusion condition, (2) a “preceding-year” exclusion condition, and (3) the OIAI (“Once In Always In”) exclusion condition. Under the first-year exclusion condition, in order to exclude the employee from making elective deferrals, the employer must reasonably expect the employee to work fewer than 1,000 hours during the employee’s first year of employment. Under the preceding-year exclusion condition, in order to exclude the employee from making elective deferrals in an exclusion year ending after the first year of employment, the employee must have actually worked fewer than 1,000 hours in the preceding 12-month period.