A meter is a wonderful thing to have. It can check the individual cells, and spot if there is one in there that is less good than the rest. Being brand new means little. It might only have been minutes between the shop shelf and being used - there is no saying how long it was between being made and sold, and waggling the cells about a bit (tech term) is as good a way of breaking down any insulating film as any. Of course, the meter is also good for measuring the actual voltage that the battery has charged to.
As Colin says, all batteries have their nominal rated voltage, will legitimately show a higher voltage when fully charged, and a lower voltage when in need of a recharge. Early NiMH cells did have a high rate of self discharge, current ones less so, but most batteries do better after they have been cycled a few times, avoiding either overcharging or over discharging. While the chemistry in rechargable cells gives a lower voltage than non rechargable types, the rechargables are generally capable of delivering more current.
Long life alkalines would typically have a capacity vastly more than Nicads, but could only deliver a fraction of the current, albeit for much, much longer. This was fine for transmitters, until the accident that everybody does, which is to leave it switched on. With rechargables, it means recharging, with alkalines, a new set.
With hindsight, higher capacity cells do take longer to fully charge. They may show a healthy voltage quite early on in the proceedings, but might need several more hours to be brimmed up.