Cannondale Synapse Neo - flats


I am thinking I want a Cannondale Synapse Neo to compliment by dMTB, however, I can no longer ride drops so am thinking fo switching to flats like a Jones bar. I know it is expensive, bur shops tell me not to do it. Is the geometry that wrong that it is not a good idea? I want an e- gravel with long range.
A year and a half ago I did the drops-to-flats swap on my Cannondale Topstone Neo Lefty 3 to try and solve my 'numb fingers' problem. The flat bar did help a lot and with one exception the swap didn't have any negative impact on the bike's handling. The one exception was when, while coasting along, I stood up on the pegs and leaned forward slightly. When I did that the steering became a bit twitchy. Nothing dramatic, but noticeable.
One thing to consider is going to a flat bar with a lot of backward sweep, like the Jones bar, will bring the handle bar closer to you. This happened to me with my swap and it made the riding position feel cramped. I could have solved this with a longer handle bar stem, but I decided to go back to a drop bar.
I really didn't like the 'feel' of the stock gravel bike handle bar on my Lefty 3, but I love my new Ritchey WCS Venturemax drop bar.

If you go with a Jones bar you will probably need, along with new brake and shift levers, a longer stem.