INTJs are supposedly rare also - I don't see them doing this (and gasp! they are tertiary Fi!).
I would & DO call it an obsession on INFJ forums...at any given moment there's at least one active thread about it & often another one stickied. Inside these topics, people take great pride in their rarity & seek to distinguish themselves from others. They make disparaging remarks about the "fake INFJs". It's pretty ridiculous.
As usual, people refuse to see a negative trait in this over-rated type, but choose to pin it on some other type when all indicators say otherwise. Maybe the INFJ forum has special snowflake syndrome because INFJs often have it?