First off he was 5'8", anyways...
You'll have few disagreeing that todays NHL player is bigger, faster & stronger. They have better gear, better nutrition, better conditioning...sports science in hockey is relatively new.
But if you're going to suggest that 1974 Sjoberg couldn't play todays game, that argument could apply to virtually any defensemen of that era. Would 2019 McDavid walk around 1978 Robinson? Quite likely.
When creating all time lists, you can only compare a player relative to their era. The degree to which one stood out from their competition is what is relevant. Sjoberg was a standout. Had he played in the NHL in his prime he would have excelled, at least on par with fellow Swede Salming.
You had a post that referenced a 4-3 win the Jets had over Pittsburgh. WHA teams played the NHL far more often than many fans realize.
1974
September
26-Houston Aeros 5, St.Louis Blues 3
28-New England Whalers 2, Philidalphia Flyers 4
29-Winnipeg Jets 1, Atlanta Flames 3
October
5-San Diego Mariners 4, California Golden Seals 3
6-Toronto Toros 3, Minnesota North Stars 5
6-Edmonton Oilers 3, Vancouver Canucks 4
6-Cleveland Crusaders 3, Pittsburgh Penguins 5
1975
No Exhibition games were played.
1976
September
21-Birmingham Bulls 7, Atlanta Flames 6
21-Houston Aeros 1, Pittsburgh Penguins 5
23-Calgary Cowboys 3, Pittsburgh Penguins 7
24-Winnipeg Jets 5, Pittsburgh Penguins 3
26-Edmonton Oilers 1, Pittsburgh Penguins 3
26-Indianapolis Racers 1, Washington Capitals 2
26-Winnipeg Jets 6, St. Louis Blues 2
October
1-New England Whalers 2, New York Rangers 2
1977
September
25-New England Whalers 2, Chicago Black Hawks 2
28-New England Whalers 5, Washington Capitals 4
28-Winnipeg Jets 1, Minnesota North Stars 2
30-Birmingham Bulls 0, Atlanta Flames 3
30-New England Whalers 7, New York Rangers 4
October
1-New England Whalers 0, Boston Bruins 5
1-Winnipeg Jets 4, Minnesota North Stars 3
3-Edmonton Oilers 3, St.Louis Blues 2
4-New England Whalers 5, Atlanta Flames 4
5-Houston Aeros 3, Atlanta Flames 5
5-Winnipeg Jets 6, St.Louis Blues 2
6-Winnipeg Jets 3, St.Louis Blues 0
7-New England Whalers 9, Pittsburgh Penguins 0
7-Birmingham Bulls 0, St. Louis Blues 4
8-Quebec Nordiques 5, New York Rangers 5
8-Edmonton Oilers 5, Detroit Red Wings 4
9-New England Whalers 4, Atlanta Flames 3
9-Edmonton Oilers 2, Cleveland Barons 4
9-Winnipeg Jets 1, Detroit Red Wings 0
10-Quebec Nordiques 5, Washington Capitals 1
1978
September
23-New England Whalers 5, Washington Capitals 2
24-Winnipeg Jets 2, St. Louis Blues 2
26-Winnipeg Jets 3, Colorado Rockies 5
27-Quebec Nordiques 3, Colorado Rockies 2
27-New England Whalers 5, New York Islanders 2
28-Birmingham Bulls 4, Atlanta Flames 2
28-Winnipeg Jets 2, New York Rangers 4
30-Quebec Nordiques 4, Washington Capitals 7
October
1-Quebec Nordiques 5, Minnesota North Stars 2
1-New England Whalers 5, Washington Capitals 1
2-Winnipeg Jets 4, New York Rangers 7
3-New England Whalers 5, Detroit Red Wings 7
3-Edmonton Oilers 4, Minnesota North Stars 2
3-Quebec Nordiques 3, Pittsburgh Penguins 0
4-New England Whalers 3, Detroit Red Wings 0
4-Edmonton Oilers 5, Vancouver Canucks 3
5-Quebec Nordiques 5, Chicago Black Hawks 2
5-Winnipeg Jets 5, Minnesota North Stars 5
5-Birmingham Bulls 3, St.Louis Blues 4
6-New England Whalers 4, Chicago Black Hawks 4
6-Indianapolis Racers 4, St.Louis Blues 1
7-Edmonton Oilers 3, Minnesota North Stars 9
7-Quebec Nordiques 4, New York Rangers 1
7-Cincinnati Stingers 6, Pittsburgh Penguins 4
8-Edmonton Oilers 6, Colorado Rockies 4
8-Winnipeg Jets 6, Minnesota North Stars 5
8-New England Whalers 4, New York Rangers 4
Overall WHA vs NHL results:
Over 67 games played the WHA won 33 times & lost 27 times to NHL clubs. There were also 7 ties. Scoring totals had the WHA 245GF to 239GA.