Generally in MEL the person at the entry to the SQ lounge reminds me that TG uses the NZ lounge but then happily admits me to the SQ lounge with a smile. Most of the time it's "welcome hgp, please make yourself comfortable and remember we don't make TG boarding announcements".
Only on one occasion did the one of the people at the front desk say "no, *A Gold flying TG J do not get access the SQ lounge when there's a designated lounge for TG". She was a bit uppity about it but her (senior) colleague intervened rapidly and sharply to correct her.
Same experience in SYD - warmly welcomed to the NZ lounge when flying *A but not SQ.