The steel outer does make the bearing stronger, an all bronze bush is easier to make though.
They are probably stating the warning as so many bushes over the years were turned out by
blokes and made of any yellowish material they had.
Some people reckon that having the shaft hard chromed and ground is a better way to go, if
that method is followed then re-lining the steel outer is great. Beware of the overall fit though,
as the case holes can be hammered out if the main has been bad for a while. I prefer the steel
versions but they are harder to find now and you are stuck with a fixed od so you can only use
them if the cases are good. Lining them with 660 is fine as an alternative. It's more work though.
As for super fine alignment, if you bolt and unbolt the cases a few times it'll change anyway.
Same as if you heat and cool them. Do the best you can, they aren't space ships.
PB1 may not be such a good idea due to it being very hard. But that's only my opinion.https://mgaguru.com/mgtech/engine/pdf/vandervell_mg.pdf