No you dont, unless you lose the combat out of synapse range 
Many times it is fairly clear that you unlikely to loose on the initial turn. All those extra attacks are quite good. Then you can move the synapse up latter.
Also anything with leaping can charge 12" (ie all hormagaunts). So I am not convinced that clustering that close to the synapse creature is all that useful. It restricts your movement options and makes it harder to get the synapse creature in good cover etc.
Anyway... I have another couple questions.
1. Codex vs. 5e Rules - The majority of the rules in my codex say something like the X biomorph provides the benefit of Y as listed in the core rule book on page (wrong number because it is a different edition).
So far so good. Actually makes sense, which is surprising given who we are dealing with.
Lictors however have a slight anomaly. They have a rule called 'Stealth' which gives them a specific benefit spelled out in my codex. The rule makes no reference to the general rule called 'Stealth' in the 5e book.
So my question is which benefit do the lictors get? The rule book or the codex?
FYI I checked the FAQ and this is not listed... (insert obscene comments about GW)
2. Biovores confuse the $#*! out of me - What size blast template do the mines use... and why/where the heck can I find this information?
I *think* it is a small blast because it doesn't say 'Large Blast' but that does not make a lot of sense because the mines detonate if within 2" of an enemy and that would mean they detonate without hitting some of the time which seems odd.
