As of June 10 2025, version 3006.102.4_0 still has the same problem even if the iptables (v1.4.21) does support the -w option. Check the last few lines of the output.
xxx@RT-BE88U-6190:/tmp/home/root# iptables -h
iptables v1.4.21
Usage: iptables -[ACD] chain rule-specification [options]...