No, they are not related.
If you are from neighbouring countries you can buy the CHF 185 (for one year) half fare card on swisspass like a swiss local (Or the GA card, but that only makes sense if you are planning to “visit” Swizterland for a whole year)
Swiss travel pass or swiss half fare card (120CHF/month) are meant for tourists and are advertised by STC. and again no, you cannot buy swiss travel pass at half the price even if you will have a swiss half fare card (120chf vers.)