Haven’t found a source that backs your numbers (and not saying they are not there, but) ...however quite an amount of that 2020 uptake could very well be attributed to the fact that those who wished to visit loved ones in aged care we’re required to produce a certificate, or at the very least declare that they had had the “flu shot” prior to moving past the front desk.
For each Care Resident you might find that there were quite a number of “flu shot” recipients who would otherwise not have been injected..
Numbers and percentages are one thing, reasons for uptake are another.
But I have no doubt you have an argument that counters that....(sigh).