I don't think so..
Some systems work fine with allow-hotplug, others don't
I'm not sure what dictates the use of auto vs allow-hotplug I guess I've never bothered to look into it.
It's probably in the man page though
Lines beginning with the word "auto" are used to identify the physical
interfaces to be brought up when ifup is run with the -a option. (This
option is used by the system boot scripts.) Physical interface names
should follow the word "auto" on the same line. There can be multiple
"auto" stanzas. ifup brings the named interfaces up in the order
Lines beginning with "allow-" are used to identify interfaces that
should be brought up automatically by various subsytems. This may be
done using a command such as "ifup --allow=hotplug eth0 eth1", which
will only bring up eth0 or eth1 if it is listed in an "allow-hotplug"
line. Note that "allow-auto" and "auto" are synonyms.
I wonder if dhclient is one of those subsystems that would use the allow-hotplug. hrmm...
The problem of using auto is that the booting gets stuck until
dhclient3 timeouts, if you lack network support while booting the
system. If you use allow-hotplug it doesn't happen.