For the second straight year, due to an NCAA rule about practice time allowed while school is in session, one team will have unlimited practice time while another will be restricted to 20 hours in the week. Last year, Ohio State was the benefactor of this stipulation, because the school's spring semester started after the National Championship, while Oregon was already in session. This year, we have the same situation, with Alabama having a practice time advantage over Clemson.
ESPN's Brett McMurphy explained the issue in an article earlier today:
This is because Alabama's spring semester starts Jan. 13 -- two days after the CFB Playoff title game on Jan. 11 (ESPN, 8:30 p.m. ET), while Clemson's spring semester begins Wednesday.
The Tigers are not restricted by the length of any practices/team meetings until Tuesday, but they are limited to a maximum of four hours a day beginning Wednesday, according to NCAA rules.
Because Alabama's spring semester doesn't start until after the title game, the Crimson Tide's countable athletic activities are not restricted by the NCAA's 20-hour weekly rule.
It is hard to claim that Ohio State won last year's title game because of this advantage, but if Nick Saban and Dabo Swinney had a choice, they would both definitely rather be in Alabama's position, as it pertains to practice time ahead of the biggest game of the year.