At least in Mikhail Gorbachev mind, NATO never said that.
According to an interview Gorbachev did with Russia Beyond the Headline. Gorbachev said NATO had never mentioned anything about moving East, at least to his recollection.
The first and last president of the Soviet Union spoke with RBTH about the past and how it should inform the present.
www.rbth.com
RBTH: One of the key issues that has arisen in connection with the events in Ukraine is NATO expansion into the East. Do you get the feeling that your Western partners lied to you when they were developing their future plans in Eastern Europe? Why didn’t you insist that the promises made to you – particularly U.S. Secretary of State James Baker’s promise that NATO would not expand into the East – be legally encoded? I will quote Baker: “NATO will not move one inch further east.”
M.G.: The topic of “NATO expansion” was not discussed at all, and it wasn’t brought up in those years. I say this with full responsibility. Not a singe Eastern European country raised the issue, not even after the Warsaw Pact ceased to exist in 1991. Western leaders didn’t bring it up, either. Another issue we brought up was discussed: making sure that NATO’s military structures would not advance and that additional armed forces from the alliance would not be deployed on the territory of the then-GDR after German reunification. Baker’s statement, mentioned in your question, was made in that context. Kohl and [German Vice Chancellor Hans-Dietrich] Genscher talked about it.
The first and last president of the Soviet Union spoke with RBTH about the past and how it should inform the present.
www.rbth.com
Now, I don't know what has been said and what has not been said, as there are no formal agreement between NATO and Soviet Union, I just don't know, but Gorbachev was there, and I inclined to take his word for it.
And just so you know Russia Beyond the Headline is not a Pro-West Russian Publication. RBTH (or known as Russian Beyond now) is owned by the same company that own RT, which is considered the State Publication as much as RT does.
en.wikipedia.org