If "provisional-distance-between-starts" is not set properly, longer <fo:list-item-label> content is shrinked or it overflow to the <fo:list-item-body> area (depending on XSL-FO processor).
There should be possibility to set this property to "auto" and to allow XSL-FO processor to compute this value according the real width of label content.
It would be helpful in cases, when <fo:list-block> element is used for single <fo:list-item>, where exact width for multiple <fo:list-item>s is not required.
With this option it would be easy to build for example TOC with nested numbered items, where width of indent is equal to the width of number part of upper level. Now it must be computed, which gives us no reliable results in every case.