Blocks fitting in 'repeat, if' etc blocks should be only those having both 'slot' and 'bump' right?

[govindamudepalli]

We know block shapes give a hint how they fit together.
I understand that the blocks like 'repeat, if ' from 'Control' blocks should be fitted with only those having both 'slot' and 'bump' right?

However I see it can be fitted with blocks that have only a bump also. For example, the 'delete this clone' block can be fitted in 'repeat' block.

Is this a bug or my understanding issue?

[mxmou]

Putting blocks without a bottom notch inside an "if" block is often useful. For example:

[JereNwa]

This is a misunderstanding.