It doesn't say that though - it says 50% of respondents to the self-selected survey which was widely shared online [probably in particular groups for women who'd been assaulted, because people want their experience to be heard and documented so are motivated to fill in the survey] , had experienced this.
You simply cannot extrapolate from that to 50% of women generally. I work in health and social research and training constantly reminds us that this sort of survey proves nothing. What it does is shows us an area which needs proper research in future. But without randomised sampling, it is of limited use.
It's like sharing the results of a mumsnet AIBU poll and saying "75% of women say LTB".
Here's what the article said, for those who don't want to click through :
survey asked more than 22,000 women if, for example, they had ever been spat at, or strangled, kicked or bitten. It also asked respondents if they had ever woken to their male partner having sex with them or performing sex acts on them while they slept. To this question, 51% answered yes.
This was not randomised sampling – the survey was widely shared online and participants were self-selected. For this reason, it’s hard to extrapolate from the findings.