There certainly can be legitimate functional reasons/purpose for basins to be required set appropriately in relation to the wall to suit the selected wall spout setup, and having experience with similar details the spout length chosen can determine the basin position and does need to be a certain length to work properly. Sometimes this requires adjustment of basin size and bench depth. In this case something's clearly happened.....without understanding the company's particular processes my guess is that the bench depth larger than what it should be. It's your home/investment, you have to live with it long term. IMO what differentiates (great from ordinary) builders is their capacity to resolve issues and shoulder responsibility when something like this occurs. Believe me they (should) have enough fat built in the profit margins to resolve these types of issues. The good news is you actually have a physical example you can refer to in the company's display home. If required go and measure it and compare it to yours to be 100% sure - in custom/boutique situations clients don't have that luxury/back-up check. Try not to play or get drawn into a "blame" game, or accept lame excuses (which the industry is expert in ;) ), it doesn't matter exactly how it went wrong, the main thing is you want to get it right/resolved. Stick to your guns ;)

our plumber correctly installed our wall mounted spouts over the centre of the basin ie water directed to the plug hole but make sure that the basin is mounted forward of the vanity and spout is shorter rather than longer as the water can spurt forward if turned on too hard by unsuspecting guests

The need to seal it attracted my attention because, while I don't know about that particular sealant and things might have improved, the issue of surfaces needing regular sealing is not very sustainably eco friendly and can have health implications. Do you know what solvent/s the sealant contains and what precautions are advised? The other question that comes to mind in relation to your actual question is, how vulnerable might the surface be as it's coming up to the time for resealing?

Harvey Norman are distributors for Timberline vanities which may have what you are looking for - see link. If you see one you like online, you can go to a HN Bathroom store and they can order it. https://timberline.com.au/