In case it helps,
last week I installed C11 and the accompanying free ‘Spectralayers One 7.0.20’ via the Download Manager. Spectralayers was installed to "c:\program files\steinberg\Spectralayers 7", the exe is version 7.0.21.250
Later I decided to try the 1 month trial of Spectralayers Pro. Initially I was a bit puzzled, after downloading it still launched as ‘Spectralayers One’. Then after reading through the above comments I realised it’s basically the same release, but to make it run Pro you need to apply the activation code. I opened the e-licenser app, added the code, it added ‘Spectralayers Pro 7 Trial’ to the e-lic, underneath where it says ‘Cubase Pro 11’. Prior to this the elic made no mention of SL 7 or SL One.
Now when I launch the desktop app ‘Spectralayers 7’ it starts the Pro7 version. So far so good.
In a month, should I decide not to buy Pro, we’ll see if the original Spectralayers One re-appears without requiring my intervention.