Every item which has own number in the shown reading order view are tagged separately. Some PDF editors which have tagging tools and "Touch up reading order" -dialog combine automatically adjacent equally tagged items under one number in the reading order view, no matter you have tagged them separately. They can still have separate tags in the tag tree. Or not. Check!
Some editors allow disabling that automatic combining, others do not.
If you have say 2 form areas that you have selected & tagged separately, but in the reading order view they became placed under same number check in the tag tree if they have separate tags.
If they happen to be included in one tag you can cut the 2nd object out of the tag and paste it as child into a manually inserted new tag. If you have Acrobat DC Pro, there's no need to cut and paste, you simply drag the object inside the tree to the right place. I have used PDF editors where the only way to change an object into a new tag is to cut & paste it as child.
If you want to keep one item out of the combined reading order area you can prevent the combining to happen by disabling the combine same -option in the Touch-up reading order dialog. If it cannot be disabled in your PDF editor, tag the item to something else, for ex. to Figure. Change it right by right-clicking the tag in the tag tree and change the tag in the tag properties dialog. Many tags require some Object attributes such as Bounding Box. Tagging to Figure at least generates it.
You cannot skip the tag tree. It's your actual battlefield - so much must be built there if you are going to build accessible PDFs which are actually accessible, not only formally right as you can easily find in make PDF accessible -guides.