Consider,
<h3 id="123">Testing</h3>
{{1x|1=odd
<h3 id="456">Testing2</h3>
asdf
asfd}}without section wrapping, the data-parsoid on the templated heading is discarded,
<h3 id="123" data-parsoid='{"stx":"html","dsr":[0,25,13,5],"reusedId":true}'>Testing</h3>
<p about="#mwt1" typeof="mw:Transclusion" data-parsoid='{"dsr":[27,79,0,0],"pi":[[{"k":"1","named":true}]]}' data-mw='{"parts":[{"template":{"target":{"wt":"1x","href":"./Template:1x"},"params":{"1":{"wt":"odd\n\n<h3 id=\"456\">Testing2</h3>\n\nasdf\n\nasfd"}},"i":0}}]}'>odd</p><span about="#mwt1">
</span><h3 id="456" about="#mwt1">Testing2</h3><span about="#mwt1">
</span><p about="#mwt1">asdf</p><span about="#mwt1">
</span><p about="#mwt1">asfd</p>however, once section wrapping is enabled, the traverser calls WTUtils::getAboutSiblings that doesn't cross the section boundaries, and therefore doesn't consider the rest of the about siblings as templated, keeping the data-parsoid,
<section data-mw-section-id="0" data-parsoid="{}"></section><section data-mw-section-id="-1" about="#mwt2" typeof="mw:Transclusion" data-parsoid='{"dsr":[0,81,null,null],"pi":[[{"k":"1","named":true}]]}' data-mw='{"parts":["<h3 id=\"123\">Testing</h3>\n\n",{"template":{"target":{"wt":"1x","href":"./Template:1x"},"params":{"1":{"wt":"odd\n\n<h3 id=\"456\">Testing2</h3>\n\nasdf\n\nasfd"}},"i":0}},"\n\n"]}'><h3 id="123" data-parsoid='{"stx":"html","dsr":[0,25,13,5],"reusedId":true}'>Testing</h3>
<p about="#mwt1" typeof="mw:Transclusion" data-parsoid='{"dsr":[27,79,0,0],"pi":[[{"k":"1","named":true}]]}' data-mw='{"parts":[{"template":{"target":{"wt":"1x","href":"./Template:1x"},"params":{"1":{"wt":"odd\n\n<h3 id=\"456\">Testing2</h3>\n\nasdf\n\nasfd"}},"i":0}}]}'>odd</p><span about="#mwt1">
</span></section><section data-mw-section-id="-1" about="#mwt2" data-parsoid="{}"><h3 id="456" about="#mwt1" data-parsoid='{"stx":"html","reusedId":true}'>Testing2</h3><span about="#mwt1" data-parsoid="{}">
</span><p about="#mwt1" data-parsoid="{}">asdf</p><span about="#mwt1" data-parsoid="{}">
</span><p about="#mwt1" data-parsoid='{"dsr":[null,79,0,0]}'>asfd</p>
</section>