Hi, just seen this thread, sorry if it has been mentioned but I don't think it has yet... I asked my consultant this a few weeks ago as I had my annual clinic over the phone but hadn't had an HbA1c done. He said quite honestly that while, yes, the libre can be inaccurate, there is also a tolerance of allowed inaccuracy with HbA1c blood tests. It is well documented to be false if you have anaemia for example. I think someone on here referenced the fact that HbA1c, libre sensors and testing strips can be within a tolerance of +/-15% of the true value. So no health care professional would ever expect them to all be exactly the same anyway.
It is also essentially a snapshot, so while the HbA1c is a way bigger snapshot and so better than just capillary glucose tests, the pattern information you get from the libre or CGMs is invaluable. He urged me to keep looking at my graphs to try and avoid spikes, as it will ultimately also aid lowering your HbA1c, even if your true values are constantly 6 and the libre is telling you 5. He said he looks for graphs as flat as possible (within good range of course) over low HbA1c.
Of course as with all tech it is only as good as the thing taking the measurement. So with capillary test you want the best strips, and with the libre I assume they are working to improve the filament function. I would assume it will improve over the years, so try to do at least a weekly capillary test to see how they compare, but love the ease of the libre and graphs it gives. I can't wait to see how my projected HbA1c compares eventually!