Totally true for very good teams. How many games were the Phillies expected to win this year -- evaluated on opening day, after the roster was set? My guess was 85-86 games. Others, I think including you, were more pessimistic than I was. A team which is not 'expected' to win 89-90 games, or more, has little leeway for things to go wrong and still make the playoffs. Every team will have slumps, including a multi-week slump. If this was the Phillies only slump of the year, then I guess no biggee, but if they turn this around within the next week, that still gives them many months for another (or more) slumps. I've said multiple times above that i believe this team will hit, at least this year and next. That's the team strength.
In general, the pitching and D look every bit as bad as we feared going into the season. I've seen nothing thus far to convince me that the 2022 Phillies are a well-constructed, reasonably balanced team. I'm convinced they aren't. This team is not good enough to blow off the first 40 games as a shakeout cruise, as you suggest. Is THIS Phillies team good enough to get hot and win 80 of 122 games at some point this season. They aren't nearly good enough at preventing the opposition from scoring to accomplish that. I'm sure some team(s) will accomplish that. I doubt the Phillies are good enough.
Another problem is we have shot our budget. There likely isn't a pile of cash to fix problems discovered during the 40-day shakeout. Also, there isn't young talent to trade, without mortgaging the future -- that's the sort of thing DD might well try to sell if the Phillies are doing well and need a little push to get over the hump. Gillick sold that.
It's not something that any GM can sell if the team is not doing well and has obvious holes, after convincing ownership to go over the lux tax threshold for first time ever. That was DD's one shot of the year at winning that particular sales pitch. He might sell the need to rebuild. He won't be able to sell the need to triple down on this season.