TARANJEET SINGH Ji,
Your meaning of the word SAT is correct.
The word which probably veer AMARPAL SINGH Ji is reffering is the word SATi{there is matra Sihari with the letter T}

You may pl observe in Gurbaani the word is always "SATiNAAMu" but nowhere we find as SAT NAAMu.

So obviously there should be some difference in the referencemeanings of the words
SATi and the word SAT.In my opinion this should be critically analysed for conveying the correct meanings of the words.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/anand-sahib/2462-anand-sahib-pauri-30-a.html

Both words are in Gurbaani but their meanings can be different as per their grammtaical indications of the words.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=2462

Prakash.S.Bagga