The letter Keir Starmer wrote to does raise questions, although it is a selective quote. Here it is in full.
This guidance is intended for the current position in the UK where there is currently no transmission of COVID-19 in the community. It is therefore very unlikely that anyone receiving care in a care home or the community will become infected. This is the latest information and will be updated shortly.
Now this remained on the Gov web site at least until 12 March when there were 1580 cases reported.
So was advice changed but not updated on the web site? However, any professional reading this on 12 March would have known about possible transmission in the community and therefore there could be infections.