Excel Does Not Set Cell Height To That I Specified

Microsoft Excel for Microsoft Office 365 MSO (16.0.13127.21886) 32-bit
Windows 10 Version 20H2 (OS Build 19042.1526)

I want to set celll height to exact 1cm.
1. View - Workbook Views - Page Layout, so Excel shows rulers.
2. File - Options - Advanced - Display - Ruler units = Centimeters.

3. Page Layout - Page Setup - Page - Print quality = 600dpi.

4. Select some cells and perform Home - Cells - Format - Row Height, input 1cm.

Perform step 4 again, Excel shows the cell height is 0.99cm, not exactly 1cm.

By visual inspection, Excel ruler shows the cell height is about 0.9cm.
Print this sheet, and measure it with a physical ruler. The cell height is about 0.9cm.

Why Excel does not set cell height to that I specified?