Catkins - after my mum had called me I thought I would get to the bottom of it and managed to get through to the doctor in charge of my dad.
He was most distressed to learn of the effect that his call had had on my mum and full explained to me that that wasn't his intention. Just standard procedure to have a discussion about possible outcome scenarios. He explained that because my dad is a 'vulnerable' patient (on account of his cardiac situation), that they had to consider all possible outcomes. However, for the present my dad is progressing and all the post-op tests are positive so far.
Best of all, an hour after my call, he got back to me to say that due to no prevalence of the virus in the ward, he would relieve some of the restrictions so that my mum can go in and visit daily. That will benefit my dad (and the hospital staff) as her presence will definitely reassure and encourage his recovery. He then called my mum to give her the good news. Unfortunately, my dad is not mobile phone or tech savvy (he struggles with the TV remote and is the original BT phone dad) and we did try the tablet Facetime option but it confused him even more. Still dealing with a little post-op delirium. My mum's physical presence will do him more good.
Establishing a report with the doctor has definitely improved the situation and he was very sweet and considerate.