Here are my personal thoughts, which could be incorrect as far as trail building doctrine are concerned.
I don't see a problem with stacking a few decent sized logs in front of a big logover. By big I mean like 12 inches or more but probably more like 18". For the smaller logovers the stacked logs are in no way needed. You can pretty much just roll the log with minimal skill. The small size diameter branches needed to stack in front of smaller logs are fragile and don't hold up for very long. They don't stay put and become a liability in short order.
As someone who has a pretty practical bunny hop in my bag of tricks I can say one of my biggest pet peeves is coming to a small logover and having to deal with a bunch of small broken sticks laying all over the trail on both sides of the log at a time when I would really want clean trail on both sides. This is a prime example of totally unnecessary and, in my opinion, detrimental stick piling as this log can pretty much be rolled with minimal skill.
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Now here is an example of a sturdy logover that does warrant the stacking of a few smaller logs on each side. This log could only be hopped by exceptionally skilled riders so the logs are a help. The logs used are also of a sufficient size and weight as to not move when the obstacle is ridden.
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Again, just my $.02 and not based on any actual trail building doctrine.