When the IRS releases a delayed Federal refund and adds some interest to it, does the refund then usually come on a paper check instead of direct deposit?

My timely efiled 2020 tax return was held up in processing at the IRS for 8 months for some unknown reason.  I presume it was eventually manually reviewed, which was odd since I don't claim any dependents, any credits, and no stimulus, and everything matched on my Wage & Income Transcript.   They never sent a letter/notice so I don't know what they were looking at.  But in any case they didn't make any changes, and I finally got all of my expected refund last month plus a small amount of interest.

 

My question is this:

I've used direct deposit for years, and this one came by paper check instead.   The WMR tool never mentioned a direct deposit at all, so I doubt one was attempted, and there would have been no reason for one to fail that I can see on my end.  Once approved, the first mention of the refund on WMR was that a check was to be mailed.

 

I realize the IRS can do that for unexplained reasons, but I'm wondering in my case it was this:

In the memo section of the check it had an annotation for the refund amount, and it had an annotation for the small amount of interest.   I'm wondering if that is the reason they sent a paper check--so that they could annotate and explain what the extra amount was for--the interest.

Does everyone who gets interest on top of a delayed Federal refund get a paper check in order to show that annotation, or am I just "special?"