Paragraph spacing from table style is not exported for each paragraph inside the table. The table style defines paragraph properties which should be respected when exporting the styles to HTML.

Workaround: Apply the paragraph settings coming from the table style directly to the elements.
foreach (var table in radRichTextBox.Document.EnumerateChildrenOfType<Table>())
{
    foreach (var paragraph in table.EnumerateChildrenOfType<Paragraph>())
    {
        paragraph.LineSpacing = table.Style.ParagraphProperties.LineSpacing;
        paragraph.LineSpacingType = table.Style.ParagraphProperties.LineSpacingType;
 
        paragraph.AutomaticSpacingAfter= table.Style.ParagraphProperties.AutomaticSpacingAfter;
        paragraph.AutomaticSpacingBefore = table.Style.ParagraphProperties.AutomaticSpacingBefore;
 
        paragraph.SpacingAfter = table.Style.ParagraphProperties.SpacingAfter;
        paragraph.SpacingBefore = table.Style.ParagraphProperties.SpacingBefore;
    }
}