Whitespaces in the filenames proposed by the export tools are replaced with + signs

Today, when exporting a page that has whitespaces in the name, for example "Sandbox.Test page with space.WebHome" , the whitespaces in the filename proposed by XWiki are replaced with + signs (for example, Sandbox.Test+page+with+space.WebHome.zip , for html export). This "encoding" is arguably a good choice:

• why cannot the whitespaces stay whitespaces? they are valid characters in all modern file systems
• if they need to be replaced, why not replace them by _ as we're replacing other special characters in the filename?