AFAIK, the property is not used anymore (its deprecated because we don't
throw an error if somebody configures it in the xml, we just ignore it)

Instead there is an interleaving property that has the opposite semantics.

This is to avoid the FAQ where people try to use an XA rar that hasn't been
coded to support interleaving, but we used to enable it by default (now we don't).

i.e. the old track-connection-by-tx behaviour is now the default for both local and xa
but you can enable interleaving for XA.

local transaction rars must always be interleaving=false, so we ignore
interleaving=true for local as well. ;-)