Mmmm.... I'm surprised. I'm sure I've done this on 1.9 and it works absolutely fine. The HTML block, AFAIK, is actually a particularly simple case as the content is just serialised in the block's database record - no additional db table(s) for that block to complicate things.
I have a hunch something else might be going wrong here. Have you run with debugging on?
Blocks
Import html from custom block in 1.9.2 - Not available?
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