I'm not sure I agree with the level of adjustment being a negative here. The point they are making is that have adjusted for confounders ie. considered other covariates (all those listed) and the results still show their exposure (VILP) being associated with their outcome of interest (mortality). It's usually better to account/adjust for as many confounders as possible (happy to be corrected by someone on this!), especially those that are clinically relevant. Usually, more covariates in the model takes it towards the null so if there is still an effect estimate, it's likely to be a better association than using crude values.
My issue with these studies from the UK Biobank though is that the wearable devices are only worn for up to 2 weeks or so, although the follow period is significantly longer in this study. For this study the "participants were required to have at least three valid monitoring days, with at least one of those days being a weekend day". Would be better to have a prospective cohort but good to see associations so further studies can investigate.