Today I was able to check my systems and can at least confirm that yours and mine works equally, I get the same error messages if the count is done from the transfer orders.
LI15 allows some analysis, but you cannot dig into the "inventory document" itself, but you can get the TO number from there, and then you can use LT21 to check the document in detail.
SAP checks the existence of the document in table LIKP only when you want go into the detail, probably a design gap, maybe for performance reasons.
At least the TO count is considered in the progress overview LX25