I do not see this as a shortcoming by any means, on either plug in. For one thing, it keeps you from salvaging something accidentally that you may have in your pack, especially if you hit the hotkey for "salvage" accidentally. You can easily sidestep this issue simply by putting the items in a house chest, and then looting them with the character you wish to salvage them on. Both plug-ins will flag them upon opening the chest, and you can easily loot the items and THEN salvage only those items it flags.
Think about it, say you had a nice major (or many) on the salvaging char you dumped all your stuff on, and you hit the salvage key, if the plug-in hasn't flagged those looted items, then it is just going to salvage every single item on the char. NOT a good thing at all. It is unreasonable to expect the plug-in to know you're transferring loot to another character using the "Give" button (or by dragging items) and know to salvage only those items, and nothing else. Now, you may have your 5 Aug'd character completely empty and know it has nothing of value to salvage, but not everyone would or could do such a thing.
Both plug-ins are very careful to protect your items, and even then, occasionally you can still end up salvaging something that may have value to you, or others. (Due to a user error with setting proper rules, but the fact remains, the only way to be 100% sure is to salvage manually.)
Simple work-around is to simply use a house chest to transfer salvage. Even if it means you have to fill it up a couple times, it is worth the extra effort if you don't want to salvage manually.
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Ling Mei - Veteran Swordswoman

Lingie - Abu's Health-Addicted Support Mage
Directionally Impaired in AC since 1999
The sun itself sees not 'till heaven clears.