Yes, every line holder could SAP Christmas off. Most do. Some guys do actually like working Christmas and keep it on their schedule.

Round 2 and reserves work it.

This is one of the reasons that seniority is important, especially if the company is hiring a lot of pilots. If you are at the beginning, you can be a line holder much faster, upgrade much faster, and have a much better quality of life. 2 or 3 months can make a huge difference.