Z Offset Layer 0 feature resets before actually starting to print it

[spitfire]

I'm using this plugin with Creality Ender 3 v3 KE and tried setting both the Z-offset, and z-offset for first layer. For a moment a z-offset being combination of both appears, then my printer starts printing a test line on the side of the bed, and after that it reverts z-offset to the value I've set, without the addition of the 1st layer one.
My start G-Code looks like this:

;Nozzle diameter = {machine_nozzle_size}
;Filament type = {material_type}
;Filament name = {material_name}
;Filament weight = {filament_weight}
; M190 S{material_bed_temperature_layer_0}
; M109 S{material_print_temperature_layer_0}

M220 S100 ;Reset Feedrate
M221 S100 ;Reset Flowrate

G28 ;Home

G92 E0 ;Reset Extruder
G1 Z2.0 F3000 ;Move Z Axis up
G1 X-2.0 Y20 Z0.28 F5000.0 ;Move to start position
M109 S{material_print_temperature_layer_0}
G1 X-2.0 Y145.0 Z0.28 F1500.0 E15 ;Draw the first line
G1 X-1.7 Y145.0 Z0.28 F5000.0 ;Move to side a little
G1 X-1.7 Y20 Z0.28 F1500.0 E30 ;Draw the second line
G92 E0 ;Reset Extruder
G1 E-1 F1800 ;Retract a bit
G1 Z2.0 F3000 ;Move Z Axis up
G1 E0 F1800

is there something in it messing with this plugin (if so please tell me what, and if I can safely disable it), or is it a bug?

I think it's doing this after drawing the test lines:

G1 X-1.7 Y145.0 Z0.28 F5000.0 ;Move to side a little
G1 X-1.7 Y20 Z0.28 F1500.0 E30 ;Draw the second line

is it the G92 E0 ;Reset Extruder command?