Yes. Bit of semantics here, but by saying 'conducts an ATPL skills test' you are implying that all the things required for the ATPL skills test that are not included in an OPC would be done. (i.e. some stuff which would also be in an LPC + the manually flown raw data ILS).
The way it was done for me was that I turned up for my sim, can't even remember whether it was an OPC or LPC, and said that I was able to unfreeze my licence with an ATPL skills test. Over the course of the 2 days we just made sure we ticked all the boxes both for the OPC and the ATPL skills test. i.e. we didn't finish the LPC/OPC and then say 'right, now for the ATPL skills test'...
(Of course, this is probably completely a function of which TRE you get on the day, some are probably more clued up about the requirements than others due to the fact that it is a relatively (under JAR) new requirement to have the ATPL LST)