I know that, say, on Unix/Linux, some filesystems do not routinely support the updating of file timestamps.   The calls appear to work but do not actually do anything.   The stated reason is efficiency:   updating file labels involves a lot of disk I/O and creates “hot spots” in those areas, forcing networked systems to do a lot of cache-invalidation for essentially no good purpose.   Usually, this behavior is configurable through some kind of knob.   My educated guess is that such a thing might be happening here.