My only objection to swinging the float bowel fore and aft is that the carburettor is set at an angle so any such repositioning will put the float bowel out of vertical, particularly noticeable on the nearside/offside axis.
The poor old needle valve already has more than enough to cope with on a bike, setting the bowel and thus the needle at an angle is just adding one more possible complication that I’d seek to avoid.
Wear, (I exclude ”adjustments” here!), of the needle valve is less of a problem than might be thought, even with marked evidence of wear it will only result in a hundredth or two of an inch rise in fuel height. If you doubt me do the maths!
For all that wear at the needle valve can be a problem; it is possible that it will not be entirely even leading to incomplete or erratic sealing. Certainly as a land forms the already small pressure per unit area for sealing falls compared with a line-on-line sealing and where there is a land then foreign bodies can get attached.
Mark you there is no need for a new groove, it occurred to me that by far the simplest way to adjust height is to place a lightweight spacer under the needle clip thus raising the needle relative to the float.