is it common, when having a mental shift to a fictotype, to have your likes and interests change?

Its pretty common, yes. A mental shift will make your mind/persona change back more in align with your kinself. 

Keep in mind if a ‘shift’ causes you to lose time, become seriously disoriented, changes your memories entirely, or seems to change who you are on a fundamental level, you may want to consider that this is not a kintype shift, but may possibly be evidence of switching with a headmate/soulbond instead.