lm0 at isa vs. lm0 at wbsio at isa

[Edgar Fuß]

What's the reason for wbsio(4) to existxs, i.e. what's the advantage of
        wbsio*  at isa port 0x4e
        lm*     at wbsio
over
        lm0     at isa? port 0x290 ...
?