Under the current system, the 1 seed doesn't know who they are even going to play on Sunday until Friday. That is a pretty big disadvantage for being the team with the best record.
By Tuesday night, the Bucks knew they'd probably be playing Miami, maybe Bulls/Raptors on Sunday.
By Wednesday night, the Bucks knew they'd probably be playing Miami, but maybe the Bulls on Sunday.
When the game rolls around on Sunday, the Bucks have home court advantage, had a week off, while whoever their opponent is will have to travel to Milwaukee having just played a win-or-go-home game <=48 hours ago. I think that's a much bigger advantage for the Bucks than not being certain which of 2 teams they'll face.
Or if comparing the #1 seed advantage to the #2-#4 seeds, where #2 has 3-4 days to prep after Tuesday play-in for Game 1, and #3-#4 have a week (if not more) to prep Game 1, isn't the advantage nullified because their opponents have the same amount of time to prepare?
When you consider the Bucks opponent will have had no time to game plan and won't be rested, I don't see the Bucks situation as a big disadvantage. More of a very slight annoyance.
On a related note though, I do always wonder how a team does game plan for a formidable unknown opponent, like the 2019 Bucks finishing off the C's in 5 going into ECF waiting on the Sixers/Raptors 7 game slug fest to end. The Bucks had 4 days off when they didn't know who their opponent would be, so are they game planning at all for Embiid/Butler/Simmons or Kawhi/Lowry and co.?
(and I think they could do it ahead of time i.e. Milwaukee give us your order pending results, Boston give us yours, etc. so some of the match-ups could be decided earlier than Friday).
In most years (outside of the last 2, which I'm not sure is the new norm or an anomaly), the #1's preferred opponents in order would probably be #10, #9, #8, #7, #6 So even with this change, they still wouldn't know who they would be facing until after Friday night the majority of seasons.
If you really want to give the Bucks advantage (besides a week off, home court throughout, and matched up against the easiest seed 90% of the time), I think you should just move their Game 1 to Saturday forcing their opponent to play a back-to-back. The Bucks would have even less time to game plan, but the bonus of a tired opponent should far outweigh that. (Though the TV partners might not like increasing the odds of a blowout, and the players won't like the idea of b2b).