So, 3 mins of faffing on the ladder and the new Energrizer (tm) LED is in. It says on the packing "30W > 72W replacement. 3000 lumen", and has a stripe up one side that should face the fitting.
Switching it on revealed instant light, however whilst it states 3000 lm, it was easily as bright as the new fluorescent I put in a year ago, and much brighter than the 15 or so year old one still in one of the fittings.
So, whether it is some clear alignment of the LEDs to direct the light, or some weird way of measuring/calculating lumens from a conventional omnidirectional tube, however it appears LED lumens are much brighter than fluorescent ones.
I replaced all the 100W incandescent bulbs in my house with the Screwfix LAP 9.5W, 806-lumen bulbs linked below, which currently cost around £9 for a pack of 5 - https://www.screwfix.com/p/lap-bc-gls-led-light-bulb-806lm-9w-5-pack/5894t
to be a direct replacement for 60W incandescents, and that's what's pointed out on the link above, but I'd read lots of user-reviews on the above Screwfix page from people who were over the moon to find the real-world LED brightness was actually equivalent to the 100W bulbs they'd too replaced, and so I was happy to give them a go, and they were right - they really are as good as the 100W bulbs they replaced even though they're sold as 60W equivalents...
Like you, I suspect light-directing improvements to be one of the main reasons behind this, although there may be other aspects in play somewhere, but I just wanted to say that your experience comparing previously-installed lumens with the newer LED-delivered lumens was also something I've seen too, when replacing my 100W bulbs...
As an aside, I've also been very pleased with the longevity of the above LED bulbs as well, which of course isn't something we discover until much later after purchase, and with them being dimmable as well, I think they're great value for money for anyone looking to replace any old 100W bulbs if they've not already done so...