A resposta foi mais óbvia que eu pensei!
Use apenas o ArrayFormula:
{ImportHtml(I1,"table",1);ImportHtml(I2,"table",1);ImportHtml(I3,"table",1);ImportHtml(I4,"table",1);ImportHtml(I5,"table",1);ImportHtml(I6,"table",1);ImportHtml(I7,"table",1);ImportHtml(I8,"table",1);ImportHtml(I9,"table",1);ImportHtml(I10,"table",1)}
ou:
=ArrayFormula({ImportHtml(I1,"table",1);ImportHtml(I2,"table",1);ImportHtml(I3,"table",1);ImportHtml(I4,"table",1);ImportHtml(I5,"table",1);ImportHtml(I6,"table",1);ImportHtml(I7,"table",1);ImportHtml(I8,"table",1);ImportHtml(I9,"table",1);ImportHtml(I10,"table",1)})
Em Ajuda do Editores do Documentos :
ARRAYFORMULA
Enables the display of values returned from an array formula into multiple rows and/or columns and the use of non-array functions with arrays.
Sample Usage
ARRAYFORMULA(SUM(IF(A1:A10>5, A1:A10, 0)))
ARRAYFORMULA(A1:C1+A2:C2)
Syntax
ARRAYFORMULA(array_formula)
array_formula - A range, mathematical expression using one cell range or multiple ranges of the same size, or a function that returns a result greater than one cell. Notes Many array formulas will be automatically expanded into neighboring cells, obviating the explicit use of ARRAYFORMULA.
Pressing Ctrl+Shift+Enter while editing a formula will automatically add ARRAYFORMULA( to the beginning of the formula.
Veja também Uso de matrizes no Planilhas Google .