[BUG] SanityCheck reports error when GRID_MAX_POINTS_X is set to 2

[JudithRichardson]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

I am using a Lulzot Taz6. I am trying to update to the latest Marlin version (bugfix-2.1.x) from an older version (2.1.1). The Taz uses the nozzle as the probe, and needs to do bed levelling by probing on 4 washers in the corners of the bed. I do not have a BLTouch on this machine.
I need to use AUTO_BED_LEVELING_LINEAR to probe at these four specific positions. I have set the PROBING_MARGIN_* variables to specify these positions relative to the X/Y_MIN/MAX_POS and X/Y_BED_SIZE values.
In the older version setting #define GRID_MAX_POINTS_X 2 compiles without complaint, and the code runs fine on the Taz, probing at the intended 4 points.
In the bugfix-2.1.x SanityCheck.h has
#error "GRID_MAX_POINTS_[XY] must be between 3 and 255."
which kills the build

Bug Timeline

This seems to have changed some time between 2.1.1 and 2.1.2

Expected behavior

I expected it to continue to compile with GRID_MAX_POINTS_X 2

Actual behavior

Fails to compile

Steps to Reproduce

#define AUTO_BED_LEVELING_LINEAR
#define GRID_MAX_POINTS_X 2
try to compile in VSCode

Version of Marlin Firmware

bugfix_2.1.x

Printer model

Lulzbot Taz 6

Electronics

stock electronics

Add-ons

No response

Bed Leveling

ABL Linear grid

Your Slicer

Prusa Slicer

Host Software

Repetier Host

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

I haven't included the full configuration files since you can reproduce this by just changing 2 lines in the distribution files

[ellensp]

was added in #25831

[thisiskeithb]

Fixed in #26199

[github-actions]

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