Scottish Labour is the source of the above hysterical claim but as is typical there is no evidence for it.

Research by Edinburgh Napier University in 2015, found:

It has been shown that despite the dominant view that the census is valuable, policy-makers are not necessarily closely engaged with the census for directing the development and implementation of policy. Those who contributed to the study provided a number of explanations for this. An external (who admitted that he was a “light” user of census data himself) drew attention to the core problem here: the census is a fundamental societal asset, albeit one that is not exploited as it should be. It thus does not meet the aspiration of its official stated purpose of supporting the delivery of public services.

https://www.napier.ac.uk/~/media/worktribe/output-169137/the-census-as-an-informationsource-in-public-policy-making.pdf

Where did Scottish Labour get the idea from? The New Labour government in 1999.

What will the SNP Government actually do for the poor? More than Labour ever did. See, for example:

https://talkingupscotlandtwo.com/2020/03/26/scotland-keeps-persistent-child-poverty-lower-than-in-england-or-wales/

https://talkingupscotlandtwo.com/2021/12/17/snp-council-goes-even-further-on-child-poverty-measures/