Warning: extra care has been taken

Asda's smoked salmon trimmings have this warning on the packet:

Warning: Extra care has been taken to remove bones, although some may remain. 

If you scroll down a bit at the link, you can see it there. For most of the time it took me to make smoked salmon crostini this morning, I was trying to work out why I didn't like this phrasing. Eventually, I worked it out, and I think it's a real-life example of the misunderstanding that conjunctions and subordination work in different ways that I'm constantly correcting in my students' work.

Our online marking software allows you to create comments that you can use whenever you need them. Here's the one I created for this:

Whereas: introduces a subordinate clause (usually before the main clause). It is not followed by a comma, but the clause it introduces is. It therefore looks like this, where X and Y are complete sentences:
1. Whereas X, Y.
2. X, whereas Y.
And it does not look like this:
3. X. Whereas Y.
Although: works exactly like 'whereas'.
However: Unlike 'whereas' or 'although', when followed by a comma, it can introduce a sentence. Also unlike them, it cannot join two sentences unless you also use a semi-colon. If you're trying to do this with 'however', you probably want 'but'.
It looks like this:
1. X. However, Y.
2. X; however, Y. [but I would recommend 'X but Y' instead]
It does NOT look like this:
3. X, however Y.
4. X however, Y.
Therefore: works exactly like 'however'.

The substitution of however for but is the one that annoys me the most: it's pure 'big word syndrome', and sounds clunky.

Back to the salmon, they've used although when but would have been better. That would have given them the precise meaning they wanted to convey, namely that even though they've been totally diligent, there might even so be some bones in the salmon. That would work because but coordinates two clauses, so neither clause 1 (extra care has been taken to remove bones) nor clause 2 (some may remain) has more importance than the other and the whole of clause 1 and clause 2 together is interpreted as the warning.

The problem with although here is that it subordinates the clause that it introduces. In their formulation that's clause 2 (some may remain). This clause, because it's subordinated, can't be the main bit of that sentence and therefore can't be the warning. Only the main clause can be the warning, and the main clause is the one that's not subordinated, namely extra care has been taken to remove bones. They're warning me that they've taken extra care to remove bones, and as some extra information they note that some may remain. That's not right! If they really wanted to use although, they could have: they just need to make the warning be the main clause and although subordinate the real extra information (their claim of diligence):

[Although extra care has been taken to remove bones,] some may remain.