Is it still a sintered base?

Yes it is.

Mr Urs Geissbühler has been quoted by Leonid Kuzmin and also there by
Alan Shepard : http://www.escnordic.org.uk/ (Myths, then pores)

....

So I wrote to , which is their email address, asking about pores. The relevant part of my email said "According to a posting on the internet by Urs Geissbühler there are no pores in press sintered running bases. Can you confirm this?". I received a reply from the man himself -

Urs Geissbühler
Chemical Engineer
Research & Development Manager
IMS Kunststoff AG
Rütimoosstrasse 5
CH-3076 Worb
SWITZERLAND


in which he said,

"there are absolutely no pores in press sintered UHMWPE base material."
......