I’m sure it’s usually advised against presumably because of the worry about disease being spread.
For practical reasons I’ve done it a few times, mainly because a particular variety has weakened or performed poorly and I’ve wanted to fill gaps. In one case I have a mixture of varieties coming up in that location but that doesn’t worry me. In another case the new ones haven’t really thrived either, presumably affected by whatever plagued the first batch. In a third case it’s worked very well.
So perhaps a bit of risk attached, but often lack of alternatives makes it worth a go.