Hi Maggie. I do MCA assessment for Court of Protection proceedings and my approach varies depending on the issues at hand, who are parties to the case and the person at the centre of proceedings. There is no right or wrong way to approach these matters, what is important is being open about the rationale for why an assessor decides to approach it in a particular manner and how they will ensure the person is properly supported to enable them to engage in the process of assessment.
I’d suggest exploring with the social worker why they want to approach it in that manner, how they will ensure a robust assessment considering the triad approach (information from the person; information from people who know the person well and information from records). See here for helpful guidance that the social worker should be following https://www.39essex.com/our-thinking/newsletters/mental-capacity-guidance-note-assessment-and-recording-capacity/
The scrutiny will come from the review of the assessment report and if necessary questions of the assessor in an oral hearing. Where concerns continue to pervade the Court might consider instructing an independent assessor/expert witness.
I hope this is helpful to you and that the matters become resolved for your partner.