Where I work at 12 and below (we only do a small fraction of the 12 year old games) they typically allow this weird (to me) practice, but once they are playing Babe Ruth (or above) it is not allowed.
When I started working games at this level I would ask about rules differences and they always say there are none, then this would come up and they would tell me it's ok. I just had to ask the coaches why they didn't mention the rules difference. I can work with whatever rules they tell me are in effect but not telling me what the rules are is a little unfair and tough to work with.
BTW I do understand the safety aspect of this rule as it is normally only used with much younger players (12 and below) and as they are normally not playing on 90' diamonds their on-deck batters only have 15'-20' if they are backed up against a fence, I just wish the coaches would mention stuff like that if asked for rules differences, most of us work games under 2-5 rules codes during the year with all sorts of little "local" rules thrown in just for "fun".
Stuff like that reminds me of working Pop Warner football in its first season locally (we have another youth football group as well), we ask both coaches before the game what rules differences there are from NFHS rules as the league did not provide our association with a rule book. They go over some point differential rules, and the first half goes off without a hitch. Then in the 2nd half one team brings out a football that looks like an arena football, gold ball with some odd looking black stripes (they had previously been using a regular looking HS football). I don't allow it and the team freaks out. I go over to talk to the head coach and ask him why he didn't mention the ball before the game and he said he didn't know there were any rules about the ball in the rule book.
Apparently the football was the 'official Pop Warner' football and perfectly legal, after confirming that by talking to both coaches, it still stuns me when I ask for rules differences and there is something so obvious and it doesn't get mentioned. Then we enforces the "normal" rules we get yelled at.
Jasper