Dose rate matters. Ion species matters.
The paper does not specify if the dose was delivered in a single fraction or if it was given over some longer period of time.
Cells repair in eight to twenty four hours if the damage is not overwhelming.
The ions used are very heavy ions, where cosmic rays and solar wind are primarily high energy Protons.
Protons have a lower relative biological effect and damage DNA in a different way than heavy ions (single stranded breaks vs. double stranded breaks).
This was not an experiment that accurately represents the quality and dose rate that travelers to mars would experience.
We already know that whole brain irradiation causes harm in humans, especially in children.
The question should be: With radiation of the kind and dose rate and duration that would occur on a mission to mars, how would the travelers be harmed.
It would be better to use Proton irradiation, once per day in relevant quantities over a period of several months and then evaluate response.