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As my consumption was enough to be well below 50USD whether or not the calculation should have included service charge/tax, I did not need further clarifications.
The mini-bar was not replenished perfectly (some consumed items not added, duplicate items placed, snacks not refilled...), and I wondered if the property really had an intention to strictly calculate consumed goods and have guests pay extra charges.
The invoice upon check-out contained no info about mini-bar charges and I was not asked to fill out the declaration form of mini-bar usages which I believe is usually needed to agree on billing.
If the property is going to strictly follow the rule, I guess in some situations this might cause a problem; There should be a process by which the property and guests agree upon what has been consumed and what the extra charge will be...

Having said that, interestingly enough, at a property in Japan, on check-out I received an invoice including the mini-bar charge with no deduction at all
The invoice was modified soon after I pointed out the mistake, but my friends, watch out for the invoice as the staff are not yet accustomed to the rule, it seems.

By the way, at properties in Japan (not sure if this applies to all properties), the cap is 5000 yen/day.
OK, the figure is easy to understand, but 1USD = 100yen conversion is something different from the world we live in and that is the rate I saw only in my childhood (currently 1USD = 110yen, approx.)