Can anyone explain why COUNTA is counting apparently blank cells?

As shown in the attached sample workbook, I had case numbers in cells. Each cell frequently has multiple "case numbers" separated by semicolons, but sometimes the names also had extra spaces (usually after the text, sometimes within it). (see Original Data table in 1st tab). I had to fix this because I need to use a Case Matter Lookup table (also in 1st tab) to find "matter names" from "case numbers," but any extra spaces stop MATCH, VLOOKUP, etc. from working. Finally, I wanted to use COUNTA to count the number of matter names in each row.

My solution was to:

1) split the column by delimiter in Power Query (see Split_Case_Nos_at_Delimiter table in 2nd tab);

2) use TRIM to remove the extra spaces (see Split_Case_Nos_Trimmed table in 3rd tab). This also worked fine - VLOOKUP returned every matching matter name from the lookup table (subtable 1 on 3rd tab). I got rid of "N/A" values by nesting VLOOKUP within IFERROR to leave a "" (subtable 2 on 3rd tab).

But I got stuck on the 3rd step (counting the number of matter names in a row) because COUNTA kept counting every cell in the row, including the ones that looked totally blank to me. This was true whether the cell contains a formula returning a blank ("") value (as in subtable 2 of tab 3) or if I pasted value (as in subtable 3 of tab 3) to get rid of the formula. 

The only solutions I found were to either 1) select the "blank" cells and use DEL or Clear All or 2) use a unique text string in my IFERROR function that I could find/replace at one go. For the life of me, though, I can't understand WHY CountA is counting what appear to be blank cells. Does anyone have an explanation for this? Or a more elegant solution to the problem than subbing in a text string and then replacing it with nothing?