Why would Trinucleotide Repeat Expansion not be as severe in its effect as a single base addition mutation?

Question

Trinucleotide Repeat Expansion (TRE)

Answer 1

If you have an insertion in a gene that is 3, 6, 9 etc. it would add a few amino acids to the protein sequence, which would probably not cause a severe damage.

If you add one nucleotide to the gene sequence you will cause a frame shift in the protein translation and the synthesis will be damaged. In this case you'll surely get a totally different protein.

A reminder : each 3 nucleotides code for one amino acid in the protein sequence.