Yes, that is correct.
The only benefit of running a full node is for privacy reasons.
As you are not requesting to other nodes the balance of your addresses, nobody can link those addresses together by your requests only.
your privacy would be safer as you are requesting the balance of all addresses.
You're not requesting everything. You'll be asking for the entire blockchain and thereby validating it yourself and thus not having to trust anyone; SPV clients trusts their peers are feeding them accurate information. It is unlikely that it would be an attack vector for OP though, I don't think SPV clients are inherently unsafe or anything to that degree. Having a full node is definitely not only for privacy but also for your own security as well.
Did you import the PGP key of ThomasV? Did you download the correct signature file?