So your thinking is that, as opposed to an ale, the slower bottle conditioning time for a lager is leading to additional oxidisation, and hence the yeast? Interesting idea. Carbonation does certainly take longer for lagers in my experience. Would love to keg lagers, unfortunately just don't have the space currently.
The idea is to add fresh is to avoid off flavours from secondary fermentation in the bottle. If you lager for a whilecthere may not be enough yeast left to carbonate as fast as normal. You can also carbonate lager at room temperature then put them in the fridge. Hope that makes sense. There is a technique called krausening you might want to look up.
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