When truing a wheel, is it enough to only use a tension meter, and not a truing stand?
A wheel could theoretically be trued by tension alone if you started with a perfectly manufactured rim, hub, spokes and nipples and you were building a perfectly symmetric wheel.   The reality is that there are minute differences and that tolerances are not all that tight.  Not to mention that ultimately the wheel has to go into a frame that also may not be perfect (dishing).

The short answer is no.  I've had many sets of hand built wheels that were beautifully crafted and never saw a tension meter because the tension was hand checked.  But, they were built in a truing stand and were incredibly close to perfect.  Your initial presumption is incorrect.