Template report plugin : numeric values are allways text in Excel or ODS reports

Hello,

i face a issue that is an large irritant.
When making an custom template reprot via plugin, numeric values are allways convert to text (even if i use ;type=num in field's arguments) so, no calculation or croos table is possible without a large time of post-treatment (changing avery cell type....).

The worst is for Amount flieds, where html code is added, that is good for text or word, but the worst for Excel (it corrupt the file !).

Expect to be clear, i set an example :
Template :
 

result :