Framerate drops noticably when using Retopologize tool

Significant framerate drop occurs when attempting to utilize the retopologize tool on landscapes. This occurs even when the landscape has remained completely unaltered. Other landscape tools experience a 2-20 FPS drop while in use, whereas the Retopologize tool consumes ~60 FPS.

Screenshots: See Attached

Regression (no) issue (does) occur in 4.11.2

1. Open Editor (any project)
2. Modes>Landscape>Create
3. In Landscape mode, set tool to Retopologize
4. Press ~ and use "Stat FPS" console command"
5. Press ~ and use "Stat Unitgraph" command
6. LMB landscape to use Retopologize tool

Results

Framerate drops signficantly, from 120 FPS to ~60 FPS or less.

Expected

Framerate drops slightly, in line with other landscape tools

After using retopologize, significant lag while painting