In theory the offset centre does not seat properly in the centre hole and a radiused centre drill should be used etc. But in practice, if you use a revolving tailstock centre nipped up just firmly it works ok with a conventional centre drilled hole each end.
Yes the theoretical geometry is going to be off by a few thou due to the exact point of contact etc but you are never going to get a taper set just right on first go anyway, whether you use a taper turning attachment or offset tailstock method. It seems you always have to do a few test cuts then measure carefully or preferably test with a matching taper sleeve etc with lead pencil marks and observe the rubbing pattern. Very much a "try and fit" job.
I've never had a problem with offsetting the tailstock using conventional centres and centre drills. It works for me. (Although it's not something I do every day or even close to it.)
Edited By Hopper on 31/10/2018 07:37:06