However, some offensives could be more "all in" than others.
The 1918 offensives as they panned out OTL were about as "all or nothing"" as you can get. The two flanks - north of Arras and east of Reims - hardly budged. All the big German gains were in the centre. Result - an enormous bulge, with undefeated Entente armies on both flanks. Germany was, quite literally "leading with her chin", and must either break through and get total victory, or else face counter attacks which, given the wearied state in which four months of fighting had left her, was likely to mean defeat. .Essentially Ludendorff had gambled and lost.
OTOH, this is far less likely with St George. Even an unsuccessful one (ie failing to take Hazebrouck), leaves only a modest dent in the front line, rather than the enormous salients of OTL, whilst a successful one means a big advance on the flank and probably much less of one in the centre [1], so that the German line is straightened out and if anything shortened, producing gains which Germany has a good chance of holding on to.
[1] I am guessing here that even if Michael still takes place as a follow-up to St.George, it is likely to be a far more modest effort than OTL's. As a glance at the map shows, in British and French sectors alike, the first German attack was by far the most successful, with subsequent ones making far less headway. While I suppose this could be pure coincidence, my personal guess is that it ain't.