I got a ~15% improvement in mileage when I stopped doing that.
When I got the car, the conventional wisdom was to accelerate as fast as would keep the battery charging. Keep that ^ visible, which allowed full 2-bar acceleration if SOC was low.
Last year, I tried lower throttle settings, about 1.5-bar, so the car accelerated more slowly, and spent more time charging the battery (and warming coolant in winter). I soon realized that lower throttle settings increased the charge rate as well. I've since set My View up with a tachometer so I could watch RPM. Keeping it under 2,000 RPM most of the time has made a huge difference, as I can still accelerate and climb what pass for hills around here while charging the HVB - win-win-win.
You may have to open this is a new browser window to see it, but in the lower chart, "baseline" was using 2-bar, and the "Spring" and "Summer" were more like 1.5-bar acceleration (when prudent, of course)
This sounds like what I do. Also, things depend on your intended speed and your current SOC.
If my HVB is low while my intended speed is city speeds, 30-45 MPH, I tap to engage ICE, bring the pressure down to just enough to keep ICE engaged, and I do a slow burn that keeps me going at the same speed (or slowly speeding up) while charging. Once I get to a good SOC, I do another "soft" tap, engaging HVB and turning off ICE, and I either keep going at the same speed, or I am slowly slowing down somewhat, and I glide until back down to a low SOC. I make changes to technique based upon the road conditions, such as areas with known hills, places where I have to stop for signals, etc.
If I have a low SOC and I need to speed up from a dead stop, such as from a red light, I start rolling with EV up to about 15-18 MPH, then I do a brief (as brief as I can get away with, given traffic flow--usually for about 5 to 7 seconds, something like that) two bar burn with ICE. This keeps me moving with the traffic flow, or even better than that. I back off of the throttle pressure but keep ICE engaged, and I try to maintain about 1.125 bar pressure to continue to speed up. After checking with My View many times, this works out to the 2,000 RPM figure.
If I have a high SOC, I start rolling in EV up to about 15-18 MPH, then I do a two bar burn to get up to intended speed ASAP. The reason: ICE uses less gas by making a higher burn for a shorter time than it does with a lower burn for a longer time. Once at speed, I glide using EV.