The Text Columns tab of the Text dialog offers spacing in inches while the Columns area of the Properties deck of the Sidebar offers spacing in centimeters.
To see this:
Go to Tools in the Menu bar and select Options. Go to LibreOffice Draw>General. In the Settings area, make sure Unit of measurement is set to Inch. Click OK.
Right click on a text box with text in it. Select Text Attributes from the context menu. The Text dialog appears. Go to the Text Columns tab. The setting for Spacing displays the distance in inches.
Close the Text dialog and make sure the text box is selected.
Go to the Properties deck of the Sidebar. In the Columns area at at the bottom of the Properties deck, Spacing is displayed in centimeters.
I see there was something similar reported earlier: bug 106231
Arch Linux 64-bit, X11
Version: 126.96.36.199.alpha1+ (X86_64) / LibreOffice Community
Build ID: 41d96a72fc0e0a9fa35b6ac88a389473f8baedaf
CPU threads: 8; OS: Linux 6.3; UI render: default; VCL: kf5 (cairo+xcb)
Locale: fi-FI (fi_FI.UTF-8); UI: en-US
Built on 16 May 2023