Haven't seen their game but ROB needs to improve his ruckwork notably which given he has what is likely a weak midfield is doubled down on as he isn't likely to get a lot of help.
Alternatively one of Gawn/Grundy needs to drop down towards the 110-115 range and of course you have to pick which one!
I do think ROB can push towards 110-115 range.
Grundy I'm not sure on but my gut says 120 is his likely low end with 130 very possible and Gawn to me just looks and feels like 130+ so that's a big drop to get down to 120.
ROB feels like the kind of pick that really only works if there is an injury.
I think it has more to do with Martin being closer to their dad's age than their age
Martin has never been good in ruck shares, is a jump based ruck that is genuinely old and has struggled with a fair few injuries over the past few years (not costing games until last year but hurting scores). He also looked done last year.
To his credit, he looked pretty good in their scratch match but I find it hard to make a case for why they would hinder the development of English any more than they have to and think Martin is more about protecting their stud than any real comment on what Martin has himself.
Not even sold his JS would be that great or that he wouldn't be rested. Good luck if you take him though, always been a favourite of mine!