This is a known bug in Adobe's PDF Maker since forever and not a recent change. However, the MS utility to export accessible PDF doesn't have the bug so you might be confusing the two export options.
Although the PDF/UA standard requires the <Lbl> tag on the bullet/number character, accessibility isn't negatively impacted when it's missing, especially if you've used a Unicode bullet (U+2022) or other glyph. Screen readers recognize the Unicode character and voice it correctly.
The PDF/UA standard has another "error" regarding the <Lbl> tag when tagging naked lists. These are lists that do not have a number, bullet, or other character on each <LI>, such as with a list of employees, a recipe's list of ingredients, etc. In these naked lists, there shouldn't be an <Lbl> tag, just an <LBody>.
Generally, we don't bother correcting Word lists that are missing the <Lbl> tag because in most cases, the missing <Lbl> tag doesn't create an inaccessible list. But when we have the time or tools to correct them in Acrobat, we do add the <Lbl>.