Scialet 50 has an article by Thierry Guérin on the re-equipping of the Berger. In it, he says that bolts were discounted on the grounds of the abuse they receive, and resin anchors on the grounds of cost, effort and irreversibility: "Il restait la broche inox à coller, mais cela faisait un chantier énorme, très coûteux et pas vraiment réversible ...".
I imagine that the Dyneema anchors are intended to be semi-permanent, and that a visiting party replaces any that are in dubious condition, necessitating investment in a relatively short length.