Oh wow THANK YOU for asking this question because I totally forgot to mention it in my review.
Yes, it is different. There are six seals in FE:if:
マスタープルフ: Master Seal. The same thing as usual. They promote lower classes into advanced classes.
パラレルプルフ: Parallel Seal. This is a little different than Second Seal in Awakening. When you use Parallel Seal on your units, your units will transform to the desired classes and keep their current levels. Let’s say you want to change a level 15 Kensei/Swordmaster to Pegasus Knight, after using Parallel Seal, your unit will become a level 15 Pegasus Knight, instead of a level 1 Pegasus Knight.
マリッジ
プルフ: Marriage Seal. This seal makes sure married units can change classes into their S-support units’ classes. If unit is married to a maid or butler, I believe this unit can also change into a butler or maid, respectively. (I did a little experiment on Ryoma for my playthrough and he can become a butler if he’s married to Felicia.)
バディプルフ: Buddy Seal. Similar to Marriage Seal. Units can change into their A+-Supports’ classes.
チャイルドプルフ: Child Seal. This kind of seal is only for “the next generation”. Kids in FE:if can use this seal and change into a high level higher-class units.
エターナルプルフ: Eternal Seal. When your advanced-class units reach their maximum level, this seal can break the limit and unlock five more levels for your units.
[I feel like I saw another seal somewhere in the game but I’m not sure anymore……]