There’s a long story behind this, but with v0.123.0 everything in a bundle is a page resource, and if it’s a content resource (with any of the extensions above) it’s a headless Page and is no longer “blindly” copied. This change was technically and structurally necessary to enable recent improvements and future capabilities, and it elimated some confusing inconsistencies.
One of the recent improvements, enabled by default in v0.123.0 and later, is that we no longer duplicate page resources when building multilingual, single-host sites. This is a huge win which reduces build times, storage requirements, bandwidth consumption, and deployment times, ultimately reducing cost.
For those who wish to truly copy files, they should go in the static directory. That does not fit your use case, hence the revised shortcode above. Yes, the revised shortcode is longer, but only because I added some missing error checks.