From your description my guess would be that you visited the Altberg factory and experienced their rather peculiar brand of "customer service"?
In my experience the difference between the Altberg factory and Whalley Warm & Dry is like chalk and cheese. Nothing is too much trouble for the boot fitters at Whalley Warm & Dry whereas at the Altberg factory you could easily be forgiven for thinking that actual customers (who pay their wages) are nothing more than an inconvenience or annoyance to them. You are not the first and won't be the last to experience this. The staff at the Altberg factory just never seem to learn from their mistakes or improve. In my opinion it's well worth the extra mileage to travel to Whalley Warm & Dry which is why they get frequently recommended by members on this forum.
The measurements taken using the Brannock device which is widely used across the whole footwear industry will not be wrong. However only you know when a boot feels right for your feet or not and your first impression of the fit and comfort formed withing the first five minutes of trying a boot on is rarely wrong.
Altberg's measuring system is known for the closeness of the fit of their boots. This often turns out to be just too close fitting for some people to achieve what they consider to be a comfortable fit. I think most people's feet have just become so accustomed to badly fitting off the shelf mass produced footwear to the point that correctly fitting footwear now just feels odd and uncomfortable to them. It is not uncommon for customers to have to go up a half or full size to achieve a comfortable fit but two full sizes is pushing it to the point where your foot may slide backwards and forwards inside the boot which can allow your toes to come into contact with the front of the boot causing painful toe bang bruising or loss of toenails or create friction which can cause blisters.
The customer is always right and the bottom line is it's your money, your feet and your decision. Only you knows when a boot feels right for your feet. If it doesn't feel right insist on going up in half sizes until you find what feels to be a comfortable fit and if necessary try other models built on different lasts until you find the one that does.
This list of Altberg models may be of interest.
2-3 Season BootsAltberg Fremington Men's 1412g RRP £179.99 (standard last with 5 width fittings)
https://www.altberg.co.uk/product/the-fremington-mens-boot-mto/Altberg Malham Men's 1344g RRP £184.99 (A-Forme last with 1 medium width fitting)
https://www.altberg.co.uk/product/the-malham-mens-boot-mto/Altberg Keld Unisex 1428g RRP £189.99 (G-Fit last with 1 wide width high volume fitting)
https://www.altberg.co.uk/product/keld-boot-factory-stock/3 Season BootsAltberg Tethera Men's 1472g RRP £214.99 (standard last with 5 width fittings)
https://www.altberg.co.uk/product/the-tethera-mens-boot-mto/Altberg Nordkapp Unisex 1460g RRP £219.99 (A-Forme last with 1 medium width fitting)
https://www.altberg.co.uk/product/factory-stock-nordkapp/Altberg Kisdon Unisex 1622g RRP £219.99 (G-Fit last with 1 wide width high volume fitting)
https://www.altberg.co.uk/product/kisdon-boot-factory-stock/I've no particular walks planned in the near future other than occasional spur of the moment local jaunts aroud the Yorkshire Dales when time permits.