Lithium Community 18.12 Release Notes

JohnD ChetnaS could you please elaborate a bit more from a technical perspective on why the following might be slow (e.g. why the new FreeMarker method utils.sequence.copyOf(<sequence>) is necessary):

<#assign items = []>
<#list 1..10 as x>
  <#assign items = items + [x]>
</#list>

<#--
    At this point, items is a sequence of size 10,
    but accessing it may be very slow. <---- why?
-->

<#assign items = utils.sequence.copyOf(items)>

<#-- We paid the slow cost once, but using the new items sequence should be fast -->

this is a VERY common pattern and I would be very interested in understanding why .copyOf() will make subsequent iterations faster, thanks in advance!