There is no strellium in chart. A stellium is at least three planets in same SIGN within 10-12 degrees.
Ah, yes, only there are so many different explanations.It's too late and, searching for quotes would take too much time
, but, I do remember seeing at least 4 different explanations of "stellium". Namely:
1) (as you already mentioned) some authorities say that the planets need to be placed in the same sign then,
2) all planets need to be inside the same sign
and/or house and, finally,
3) all planets need to be located in the sector of 30 degrees
4) all planets involved in a stelium (regardless of what has been mentioned above) need to be in a conjunction (not more than 5 degrees away from each other).
To this I may add that I have also fund explanations saying that a stellium must have a minimum of 4 planets although I wander if this was just a typo.
Finally, some traditional astrologers would exclude the outer planets.
What you mention could have a lot to do with 1) and 4) . If the astrologer does not use across the sign aspects and wants to see all the planets in a conjunction then insisting on the same sign makes sense although, even if we did have 4 planets each conjunct another planet, we could still assume that not all planets are within the orb of multiple conjunction.
Personally, I'm fine with all of the above.
I don't see a huge importance in determining what a stellium is. If I see many planets inside the same sign,to me, that only means that the influence of that sign is strong in the chart but, how this influence will manifest in reality will depend on the combination of the energies and the dignities of the planets found in that sign.
Furthermore, if I see a crowdy house, then I examine it as the focal point of the chart regardless of the sign in which they are placed.
Just my twopence, anyway!
Cheers,
aglaya