Comparison of the SOAs of two MOSFETs
If you notice, the IRFBG30 does not have a 100ms line either.

Generally speaking, the manufacturers do not put SOA lines that do not intersect the \$V_{DS(MAX)}\$ vertical line and from inspection it appears that would be the case for the 100ms line for the IRFBG30 (it looks as if it would terminate at about 500V).

The DC line would be similarly constrained at a much lower voltage.

An interesting thing about SOA graphs; they are showing that if you can somehow hold the case temperature at 25C then the lines shown will not result in excess dissipation (Tj at 150C in this particular case) but holding the case at 25C (unless you are outside in the Antarctic and even then it might be troublesome) is nigh on impossible.

This application note from Ixys is recommended reading.