That can mean a world of difference to a build planning on wearing heavy armor. IIRC, if PCs level manually, someone should be able to afford plate armor in a shop by level 6. The p38 guidelines, for example, mean that a level 10 character still hasn't managed to get their hands on plate armor. Magic items don't intrinsically have anything to do with it, and you brought them up, not me - there are many ways to define "poorer". At least that's the way we've always done it. The easiest and IMO fairest way to apply this disadvantage is to simply reduce the amount of loot they have.
I think it's also petty common practice that when someone rolls up a new character in an ongoing campaign, whether due to death or story circumstances or even just boredom with their old character, the new character is expected to be at a bit of a disadvantage compared to the characters who have been going from the start. I would point you towards two places in the 5th edition DMG. Learn more about bidirectional Unicode characters.
To review, open the file in an editor that reveals hidden Unicode characters. A player starting at level 8 doesn't need extra items to keep the character feeling new and interesting, as opposed to someone who has played that character for months. As far as guidance from the Dungeon Masters Guide, see : Starting at Higher. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. Being generally unnecessary to reach basic performance requirements of a given level (aside maybe from needing magical weapon damage after level 6 or so) magic items are largely about character growth and progress. This is actually the first time I've run into the expectation that it should match. There are homebrew tables you may be able to find addressing this issue. Said table infamously does not match, not even a little, the guidelines elsewhere in the DMG for rewarding players as they level - instead, using the p38 table leaves the party substantially poorer than had they leveled up manually. This information is on an incredibly hard to find table in the DMG (every time I need it, I google it - none of the terms I intuitively look for in the index help locate it), on page 38.