Not calling for backup is a silly tactical blind spot to take pride in
IDK man, sometimes you just gotta bang out some headcanons about the structures the story takes place in b/c it'll bother you, and nobody else, if you don't know.
So. The Wreckers actually have three different signals that broadly fall under the category of "distress signal".
The first one is "general distress", which is consistent across the entire Autobot faction. This is the one that sees basically no use, because once the Wreckers are on assignment, it's a matter of pride of either seeing it through or dying in the attempt. They have a higher-than-average rate of response to general distress calls, though, because they can't exactly go straight from highly volatile mission to another without long planning and restocking phases inbetween, which often leaves the ground teams with jack shit to do, which leads to plenty of playing heroes because why the hell not.
The other two signals only used by Wreckers are unique variants of the Autobot "position compromised" signal. The first one is "position lost -- retreating", also known as the "they're all yours, boys" signal. Retreat signals are usually something issued to units from command, but because Wrecker plans often rely on having one team causing as big of a ruckus as they can while the other one tries to get something actually done, the deadline for getting shit done is when the other team is no longer capable of fighting. On paper, after the signal is issued you're supposed to haul aft and wait for a regroup signal somewhere safe, but in practice whoever has issued the signal is going to need extraction, having failed their own push, or because they're genuinely being overwhelmed in their position.
The other signal is "position lost -- retrieval". This one is actually more common to see, especially during missions that go disastrously wrong, because the proud fuckers that they are, most Wreckers are awful at knowing when to retreat and will only give up once they're literally incapable of getting away. The retrieval signal is the last thing any given team will send out, almost a formality, because it comes with the expectation that by the time retrieval is available, they'll be long dead.
The Wreckers also have a dedicated "converge on point" signal that is used in similarly suicidal ways and literally just designates a spot where any available unit can and should come in guns blazing, regardless of circumstance and heedless of possible friendly fire. The only other unit that uses a similar signal is Autobot Special Ops, and Wreckers and SpecOps have cordially agreed to use different signals in case one ever needs to act as a decoy for the other.