t2 is a cable all of whose variables are cell arrays. That's almost certainly not what you want.
Assigning one row at a time is sometimes not the best way to create a table, but if you really need to do that, you probably want to preallocate both the size and the data types of the table's variables, and then assign each row.
>> t = table(cell(4,1),NaN(4,1),NaN(4,1),NaN(4,1),'VariableNames',{'f1','f2','f3','f4'})
t =
4×4 table
f1 f2 f3 f4
__ ___ ___ ___
[] NaN NaN NaN
[] NaN NaN NaN
[] NaN NaN NaN
[] NaN NaN NaN
>> t(1,:) = {'001' 2 3 4}
t =
4×4 table
f1 f2 f3 f4
_____ ___ ___ ___
'001' 2 3 4
[] NaN NaN NaN
[] NaN NaN NaN
[] NaN NaN NaN
>> t(2,:) = {'002' 5 6 7}
t =
4×4 table
f1 f2 f3 f4
_____ ___ ___ ___
'001' 2 3 4
'002' 5 6 7
[] NaN NaN NaN
[] NaN NaN NaN
Note the right-hand side of those assignments. Normally, if the LHS is a parenthesis subscript expression, the RHS needs to be the same type, a table in this case. But table providea a conveneince where a RHS that's a cell array is treated as if cell2table were called on it. Because you have mixed types in each row, that's helpful.
