The automatic legend labeling in tmap_scale_intervals() shows duplicated numerical entries. See e.g. the Happy Planet Index here (https://r-tmap.github.io/tmap/articles/01_tmap_intro_v4.html#suggestions), where the number 20 can be found both in "10 to 20" and "20 to 30". For many topical maps this may be sufficient, but it presents a problem when showing maps of physical quantities (e.g. temperature) to a phyiscal science community. Also, for labeling small integers, legend labels such as "1 to 2", "2 to 3" etc. appear confusing.

Possibly this is only a matter of relabeling, e.g. in the above example "10 to <20"; "20 to <30" or similar (I suspect this is how the binning works).